JP6611750B2 - Plasma generator - Google Patents

Description

  The present invention relates to a plasma generation apparatus.

  It is known that high voltage is applied to the electrode pair to turn the processing gas into plasma, and the plasma is brought into contact with the member to be processed to perform various plasma processing such as etching processing, plasma CVD (chemical vapor deposition) processing, and surface processing. It has been.

  When such a plasma treatment is performed on a member to be treated, it is necessary to make the intensity of the generated plasma uniform in order to make the treatment uniform. However, in particular, when plasma is generated using a wide electrode pair in order to perform a plasma process on a member to be processed having a large area, the distribution of plasma intensity becomes non-uniform in the width direction of the electrode pair. There was a problem. This is because a backward wave traveling in the opposite direction to the traveling wave propagating on the electrode also exists, and by combining these waves, a standing wave having a magnitude depending on the location is generated.

On the other hand, when a wide electrode pair is used, the voltage distribution at each position of the electrode is averaged by increasing the feeding point to the electrode.
Further, in Patent Document 1, a plurality of RF supply terminals connected to a common RF power supply (high frequency power supply) are provided for the high frequency power supply, and a bias voltage at each RF supply terminal is detected to detect each RF supply terminal. It is described that the distribution of the plasma intensity is made uniform by providing a setting device that sets the voltages of the two to be equal, and the setting device is common to each RF supply terminal other than the RF supply terminal that becomes the center potential. It describes that it consists of a variable capacitor inserted between the RF power source.

  In Patent Document 2, the electrical characteristics of the cable are adjusted so that the phase difference between the feeding points is the same in the discharge electrode portion adjacent to the central portion of the substrate. By adjusting the electrical characteristics of the power supply and changing the phase difference at the feed point, and adjusting the phase at the feed point of the high-frequency power, the generation of the phase difference between the high-frequency powers fed to the multiple feed points is suppressed, and the plasma It describes that the intensity distribution is uniform.

JP 58-145100 A JP 2007-67441 A

However, the configuration of the setting device that inserts a variable capacitor between the RF supply terminal and the common RF power source and sets the voltages of the RF supply terminals to be equal to each other is costly with the variable capacitor itself. In addition, there is a problem that the size of the device is increased to secure a space for attaching the variable capacity, and the cost of the entire device is increased.
On the other hand, the configuration that adjusts the electrical characteristics of the cable and adjusts the phase at the feeding point of the high-frequency power requires that the cable be sequentially replaced after the plasma is stopped and the device is opened in order to obtain an optimum feeding configuration. There was a problem of low practicality. In addition, there is a problem that the number of types of cables to be examined increases until an optimum value is obtained.

  In addition, as described above, even if a variable capacitor is used or the voltage distribution is adjusted by replacing the cable, a fine voltage fluctuation distribution generated between the feeding points on the electrode remains. For this reason, if the required level of voltage fluctuation to be aimed at is high, a large number of power feeding points must be installed. If it does so, it will be necessary to adjust a phase with respect to each cable, and will become a complicated mechanism.

  The object of the present invention is to solve the above-mentioned problems of the prior art, to reduce fine voltage fluctuations due to standing waves, and to reduce the wave phase difference due to the difference in the length of the propagation path. An object of the present invention is to provide a plasma generating apparatus capable of easily obtaining a voltage distribution.

As a result of diligent investigations to achieve the above object, the inventors of the present invention have supplied an electrode, a counter electrode disposed facing the main surface of the electrode, and supplied high frequency power to the electrode to generate plasma between the electrode and the counter electrode. A high frequency power source to be excited, a conductor plate connected to the electrode from the high frequency power source, a grounded ground conductor disposed over the conductor plate, and at least a part between the conductor plate and the ground conductor Having a dielectric, the width of the conductor plate increases from the high-frequency power source toward the electrode, and the dielectric constant due to the dielectric decreases from the center to the end in the width direction of the conductor plate. The inventors have found that this can be solved and completed the present invention.
That is, it has been found that the above object can be achieved by the following configuration.

[1] electrode,
A counter electrode arranged to face the main surface of the electrode,
A high frequency power source for supplying high frequency power to the electrode to excite plasma between the electrode and the counter electrode;
A conductive plate connected to an electrode from a high-frequency power source,
A grounded ground conductor disposed over the conductor plate, and
Having a dielectric disposed at least in part between the conductor plate and the ground conductor;
The width of the conductor plate increases from the high frequency power supply side to the electrode side,
A plasma generation apparatus in which a dielectric constant due to a dielectric decreases as it goes from a central portion to an end portion in the width direction of a conductor plate.
[2] When the length of the hypotenuse of the conductor plate is b, the height in the direction from the high frequency power source to the electrode is a, and the relative dielectric constant of the dielectric is ε _r , 0.7 ≦ (a × √ ( The plasma generating apparatus according to [1], which satisfies ε _r )) / b ≦ 1.3.
[3] The height in the direction from the high-frequency power source to the electrode is a, the relative dielectric constant of the dielectric is ε _r , and the distance from the central axis toward the end in the width direction of the conductor plate is y. When the distance between the dielectric and the ground conductor at the position y from the center is D, and the constant k is 0.8 ≦ k ≦ 1.2, the dielectric at the position y from the central axis The total thickness d (y) is
d (y) = k × (a ² × (ε _r −1) −y ² ) × D / (a ² × (ε _r −1))
The plasma generation apparatus according to [1] or [2], wherein
[4] The plasma generating apparatus according to [1] or [2], wherein the dielectric is disposed so that the proportion of the dielectric occupying the space between the conductor plate and the ground conductor adjacent to the conductor plate can be changed. .

  According to the present invention, it is possible to reduce fine voltage fluctuations due to standing waves, reduce the phase difference of waves due to differences in propagation path length, and easily obtain an optimum voltage distribution. A generation device can be provided.

It is a front view which shows typically an example of the plasma production apparatus of this invention. It is a side view of FIG. It is the sectional view on the AA line of FIG. It is a front view which shows typically another example of the plasma production apparatus of this invention. It is a front view which shows typically another example of the plasma production apparatus of this invention. It is a schematic sectional drawing which shows another example of the plasma production apparatus of this invention. It is a schematic front view which shows another example of the plasma production apparatus of this invention. It is a schematic front view which shows another example of the plasma production apparatus of this invention. It is the BB sectional view taken on the line of FIG. It is a schematic front view which shows another example of the plasma production apparatus of this invention. It is sectional drawing of FIG. It is a schematic sectional drawing which shows another example of the plasma production apparatus of this invention. It is a graph which shows the relationship between a position and a measurement voltage. It is a graph which shows the relationship between a position and a measurement voltage. It is a schematic front view which shows the structure of the plasma production apparatus of a comparative example. It is a schematic front view which shows the structure of the plasma production apparatus of a comparative example. It is a schematic front view which shows the structure of the plasma production apparatus of a comparative example.

Hereinafter, a plasma generating apparatus according to the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.
The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In the present specification, for example, an angle such as “45 °”, “parallel”, “vertical”, or “orthogonal”, unless otherwise specified, has a difference from an exact angle within a range of less than 5 degrees. Means. The difference from the exact angle is preferably less than 4 degrees, and more preferably less than 3 degrees.
In this specification, “same” includes an error range generally allowed in the technical field. In addition, in the present specification, when “all”, “any” or “entire surface” is used, it includes an error range generally allowed in the technical field in addition to the case of 100%, for example, 99% or more, The case of 95% or more, or 90% or more is included.

The plasma generation apparatus of the present invention comprises:
electrode,
A counter electrode arranged to face the main surface of the electrode,
A high frequency power source for supplying high frequency power to the electrode to excite plasma between the electrode and the counter electrode;
A conductive plate connected to an electrode from a high-frequency power source,
A grounded ground conductor disposed over the conductor plate; and
Having a dielectric disposed at least in part between the conductor plate and the ground conductor;
The width of the conductor plate increases from the high frequency power source toward the electrode,
In the plasma generation apparatus, a dielectric constant of the dielectric decreases as it goes from a central portion to an end portion in the width direction of the conductor plate.

FIG. 1 is a front view schematically showing an example of the plasma generation apparatus of the present invention. FIG. 2 shows a side view of FIG. 1A viewed from the y-axis direction. FIG. 3 is a cross-sectional view taken along line AA in FIG. In FIG. 3, the dielectric 24 is partially omitted for the sake of explanation.
A plasma generation apparatus 10a shown in FIGS. 1 to 3 is an apparatus that generates a plasma between electrode pairs by applying a high-frequency voltage to an electrode pair composed of an electrode 12 and a counter electrode 14, and a member to be processed between the electrode pairs. Various plasma treatments can be performed by arranging Z. The plasma generation apparatus 10a includes an electrode 12, a counter electrode 14, a ground conductor 18, a dielectric 24, a high-frequency power source 30, a matching unit 32, and a conductor plate 38a.

In the present invention, the member to be processed Z is not limited, and various members can be appropriately used according to the plasma processing to be performed.
For example, when film formation is performed on the member to be processed Z by a vapor deposition method (vacuum film forming method) such as plasma CVD, the member to be processed Z is a resin film such as a PET (polyethylene terephthalate) film. It is done. In addition, the member to be treated Z has a layer (film) for expressing various functions such as a planarizing layer, a protective layer, an adhesion layer, a reflective layer, an antireflection layer, a barrier layer, etc., using a resin film or the like as a base material. It may be a film-like product formed by film formation.

  In addition, the plasma generation apparatus 10a performs a plasma treatment while conveying a long target member Z in a longitudinal direction along a predetermined conveyance path that passes between electrode pairs, so-called roll-to-roll (Roll to Roll or less). , Also referred to as “RtoR”), or plasma processing may be performed in a so-called single-wafer type using the cut sheet-like member Z to be processed.

  In addition, for example, when the plasma generation apparatus 10a is an apparatus that performs film formation by a vacuum film formation method such as plasma CVD, at least the electrode 12 and the counter electrode 14 are disposed in a vacuum chamber to perform plasma processing. When performing the plasma processing, the space between the electrode pairs may be subjected to plasma treatment with a predetermined degree of vacuum.

The electrode 12 constitutes an electrode pair together with the counter electrode 14 in the plasma generating apparatus 10a. The electrode 12 is a known electrode used in a plasma generation apparatus such as plasma CVD. In the example shown in FIGS. 1 and 2, the electrode 12 is an elongated plate-like member. Further, the discharge surface which is one maximum surface is arranged to face the counter electrode 14.
The electrode 12 generates plasma between its discharge surface and the counter electrode 14 constituting the electrode pair.

Here, as shown in FIG. 1, a conductive plate 38a described later is connected to the electrode 12 on the surface opposite to the discharge surface (hereinafter also referred to as the back surface), and supplied from a high frequency power supply 30 described later. The high frequency voltage to be applied is applied to the electrode 12 through the conductor plate 38a.
In the example shown in FIG. 1, the conductor plate 38 a is connected to the entire width direction (y direction) of the back surface of the electrode 12. That is, the entire width direction of the back surface of the electrode 12 is a feeding point 39, and a high frequency voltage is applied via the conductor plate 38a.

  The counter electrode 14 constitutes an electrode pair together with the electrode 12 and is a known counter electrode used in a plasma generation apparatus such as plasma CVD.

  As a material for forming the electrode 12 and the counter electrode 14, metals such as aluminum, aluminum alloy, iron, titanium, and stainless steel can be used. Further, the forming material of the electrode 12 and the forming material of the counter electrode 14 may be the same or different. A dielectric layer may be formed on the surfaces of the electrode 12 and the counter electrode 14.

In the case where the plasma generating apparatus 10a performs plasma processing while conveying a long target member Z in the longitudinal direction by RtoR, the counter electrode 14 is a cylindrical shape that can rotate around the central axis. It may be a member (drum). In this case, the member to be processed Z guided by a predetermined path is hung on a predetermined region of the peripheral surface of the cylindrical counter electrode 14 and conveyed in the longitudinal direction while being held at a predetermined position.
For example, in the example shown in FIG. 1, when processing by RtoR is performed, the member to be processed Z is transported in the z direction.

In the illustrated example, the counter electrode 14 is connected to the ground. However, the present invention is not limited to this, and a bias power source for applying a bias to the counter electrode 14 may be connected as necessary. . Alternatively, the ground and the bias power supply may be connected to be switchable.
As the bias power source, all known power sources such as a high frequency power source and a pulse power source for applying a bias, which are used in various plasma generating apparatuses, can be used.
In addition, a dielectric may be attached to the opposing surfaces of the counter electrode 14 and the electrode 12 in order to enhance the discharge stability.

The conductor plate 38 a is a conductive member that is connected to the back surface of the electrode 12 and applies a high-frequency voltage from the high-frequency power supply 30 to the electrode 12.
As shown in FIGS. 1 and 2, the conductor plate 38a is a plate-like member having a maximum surface of an isosceles triangle. Further, the base of the isosceles triangle (the side that is not the same) is connected to the back surface of the electrode 12, and the apex (hereinafter simply referred to as the apex) shared by the equilateral is connected to the matching unit 32 (the high frequency power supply 30). A conducting wire 21 is connected.
In addition, the length of the base of the isosceles triangle of the conductor plate 38 a substantially matches the width of the electrode 12. Therefore, the conductor plate 38 a is connected to the entire width direction of the back surface of the electrode 12.
That is, the conductor plate 38a has a shape in which the width in the y direction increases from the high frequency power source toward the electrode.

  The material of the conductor plate 38a is not limited as long as it is a conductive material, and metals such as copper, gold, silver, aluminum, aluminum alloy, iron, titanium, and stainless steel can be used.

  The high frequency power supply 30 is a power supply that supplies plasma excitation power to the electrode 12. As the high-frequency power source 30, all known power sources that are used in various plasma generation apparatuses can be used. In particular, it is preferable to use a high frequency power source (RF power source), and the frequency is preferably 10 MHz to 300 MHz, and more preferably 13 MHz to 60 MHz.

The matching unit 32 is connected to the high-frequency power source 30 through the coaxial cable 36, and matches the impedance of the high-frequency power source 30 and the impedance of the connection load of the high-frequency power source 30. The matching unit 32 is connected to the conductor plate 38a via the conducting wire 21.
As the matching unit 32, all known matching units used in various plasma generation apparatuses can be used.

The ground conductor 18 is a member having a box shape that encloses the electrode 12 and the conductor plate 38a, and a surface that faces the discharge surface of the electrode 12 is open. The ground conductor 18 is formed in a shape corresponding to the shape of the electrode 12 and the conductor plate 38a so as to be separated from the electrode 12 and / or the conductor plate 38a by a predetermined distance.
The ground conductor 18 is made of a grounded conductive material and functions as a shield member. It also serves as a current path that returns to the power source. It is also possible to function as a ground plate that suppresses abnormal discharge from the electrode 12.
The material of the ground conductor 18 is not limited, and a known material used in a conventional plasma generation apparatus such as a metal such as aluminum can be used.

The dielectric 24 is disposed in at least a part of the region between the ground conductor 18 and the conductor plate 38.
Here, in the present invention, the dielectric 24 is disposed such that the dielectric constant of the dielectric 24 decreases from the central portion to the end in the width direction of the conductor plate 38a.

  In the example shown in FIGS. 1 to 3, the dielectric 24 is disposed in each of the spaces between both main surfaces of the conductor plate 38 and the ground conductor 18. As shown in FIG. 1, the dielectric 24 is substantially the same shape as the conductor plate 38a when viewed from the z direction, and is disposed at a position overlapping the conductor plate 38a. As shown in FIG. 3, the dielectric 24 has a shape in which the thickness (z-direction thickness) of the conductor plate 38a in the width direction (y-direction) is thicker toward the end in the width direction. Have Thereby, the dielectric constant by the dielectric 24 is configured to decrease from the center portion in the width direction of the conductor plate 38a toward the end portion.

As shown in FIG. 1 and the like, when using a conductor plate whose width increases from the high frequency power supply side toward the electrode side, the length of the propagation path when the high frequency power propagates through the central portion of the conductor plate, and the conductor plate The length of the propagation path when propagating in the vicinity of the hypotenuse is different. Therefore, the phase of the arriving wave differs depending on the position in the width direction of the electrode.
Here, a so-called parasitic capacitance is generated between the conductor plate and the ground conductor. Furthermore, if a dielectric is disposed between the conductor plate and the ground conductor, the capacitance generated between the conductor plate and the ground conductor can be adjusted. Therefore, by adjusting the capacitance and delaying the speed of the electromagnetic wave given by v = 1 / √ (LC), the phase delay of the wave propagating in the conductor plate can be formed. Here, L is a self-inductance per unit length, and C is a capacitance per unit length when considering a minute width along the path of a propagating wave.
Therefore, by setting the dielectric constant due to the dielectric to decrease from the center to the end in the width direction of the conductor plate, the capacitance generated between the conductor plate and the ground conductor is reduced in the width direction of the conductor plate. It can be adjusted according to the position. Thereby, the phase of the incident wave is continuously shifted in the width direction of the conductor plate, and the wavelength of the high-frequency power propagating in the conductor plate can be shortened toward the center side in the width direction of the conductor plate. Thereby, the phase difference can be reduced by making the phase difference of the wave reaching the electrode the same at any power feeding location, regardless of how the path in the light guide is traced.

The material for forming the dielectric 24 is not limited, and may be a polymer material such as PTFE (polytetrafluoroethylene) or epoxy resin, or an insulator such as Al ₂ O ₃ (alumina) or Si ₃ N ₄ (silicon nitride). That's fine. In order to ensure a wide phase adjustment range, a material having a high relative dielectric constant is preferable, and alumina or the like is preferably used. However, glass, plastic, or the like may be used as an alternative because of cost.

As described above, when various plasma treatments are performed, in order to make the intensity distribution of the plasma uniform, the number of feeding points to the electrodes is increased.
In such a configuration in which a plurality of feeding points are provided on the electrode, in order to further uniform the plasma intensity distribution, a variable capacitor is inserted between the feeding point (RF supply terminal) and the high-frequency power source. The configuration that provides the setting device that detects the voltage at and sets the voltage at each feeding point to be equal is costly with the variable capacitor itself, and the device is enlarged to secure a space for mounting the variable capacitor, There is a problem that a mechanism for turning a variable-capacity knob is required, which increases the cost of the entire apparatus. In addition, when the variable capacitor is used under a high voltage for a long period of time, sparks are likely to occur due to the variable capacitor, and there is a problem that it is necessary to replace it periodically.
Also, for multi-point power supply, the current introduction terminal on the vacuum side must be increased from the atmosphere side, and a variable capacitor must be installed on the atmosphere side, so the length from the matching unit to the electrode becomes redundant. Cheap. For this reason, when the number of reflected waves increases for some reason, it takes time to return to a steady value, and there is a problem that the burden on the power supply is large.

  In addition, in the configuration that adjusts the electrical characteristics of the cable connecting the high-frequency power source and each feeding point, and adjusts the phase at each feeding point to make the distribution of plasma intensity uniform, in order to obtain an optimum feeding configuration After the plasma was stopped and the device was opened, there was a problem that the utility was low because it was necessary to replace the cable sequentially. In addition, there is a problem that the number of types of cables to be examined increases until an optimum value is obtained.

  Furthermore, even if a variable capacitor is used or the voltage distribution is adjusted by replacing the cable, a fine distribution of voltage fluctuations that occur between the feeding points on the electrode remains. For this reason, if the required level of voltage fluctuation to be aimed at is high, a large number of power feeding points must be installed. If it does so, it will be necessary to adjust a phase with respect to each cable, and there existed a problem that it became a complicated mechanism.

On the other hand, the plasma generating apparatus 10a of the present invention has a configuration in which the high-frequency power supply 30 and the electrode 12 are connected using a conductor plate 38a that increases in width toward the electrode 12 side. By using such a conductor plate, the distance between power supply points for multi-point power supply is as close as possible to zero. By reducing the distance between the feeding points, the interval between the standing wave generated between the feeding points and the adjacent standing wave can be reduced, and the oscillation due to the standing wave can be substantially suppressed. By using such a configuration in combination with the above-described configuration for reducing the phase difference, an optimum voltage distribution can be obtained.
Moreover, since the structure of this invention only arrange | positions one conductor plate, an apparatus can be simplified. In addition, unlike conventional models, there is no need to individually determine the length of multiple cables, the dielectric material around them, the design of the dielectric conductor coverage, etc. Development costs for controlling can be reduced.

  In addition, the configuration of the present invention has a dielectric between the conductor plate and the ground conductor, and increases the dielectric constant at the central portion by increasing the thickness of the dielectric on the central portion side. The wavelength of the high-frequency power propagating through the central portion can be shortened. On the other hand, in the vicinity of the hypotenuse, since the dielectric is thin, the dielectric constant is low, and the wavelength of the high-frequency power propagating in the vicinity of the hypotenuse is longer than that in the central portion. Therefore, it is possible to reduce the phase difference between the wave passing through the short propagation path in the central portion of the conductor plate and the wave passing through the long propagation path on the oblique side of the conductor plate.

  As described above, the configuration of the present invention can suppress the fluctuation of the voltage due to the standing wave, and can reduce the phase difference of the wave due to the difference in the propagation path in the conductor plate. Therefore, uniform plasma can be generated. Therefore, even when a wider process is performed, the process can be performed uniformly. For example, when used in a CVD (chemical vapor deposition) process, a uniform film thickness and film quality can be obtained even with a wide process. In the etching, the amount of scraping can be made uniform in the width direction.

  Further, since the conductor plate is a plate-like member, it can have rigidity, and the conductor plate can support the electrodes. Thereby, the bending of an electrode can be prevented. As a result, the distance between the electrode and the counter electrode can be prevented from changing due to the deflection of the electrode, and the electric field generated between the electrode and the counter electrode can be kept uniform.

  In addition, since uniform plasma can be generated in the width direction of the electrode, filamentous discharge (streamer) is unlikely to occur, and glow discharge is easily maintained even when input power (applied power) is increased.

  Here, in the example shown in FIG. 1, the conductor plate 38 a and the electrode 12 are connected to each other in the entire width direction. That is, the length of the power feeding point 39 is the same as the length of the electrode 12 in the width direction. However, this is not a limitation. From the viewpoint of suitably suppressing fine voltage fluctuations due to standing waves, the length of the feeding point 39 is preferably half (50%) or more of the length of the electrode 12 in the width direction, more preferably 75% or more. Preferably, it is most preferable that it substantially coincides with the length of the electrode 12 in the width direction.

  In the example shown in FIG. 1, the conductor plate 38 a has an isosceles triangle with a maximum surface shape, but is not limited thereto, and the width of the conductor plate 38 a is from the high frequency power supply 30 side toward the electrode 12 side. What is necessary is just a shape which becomes large. For example, like the conductor plate 38b of the plasma generation apparatus 10b shown in FIG. 4, the side from the high frequency power supply 30 side toward the electrode 12 may be curved. Alternatively, a shape in which the width gradually increases from the high frequency power supply 30 side toward the electrode 12 side may be used. From the viewpoint of suitably suppressing fine voltage fluctuations due to standing waves, the width of the conductor plate is preferably a shape in which the width continuously increases from the high-frequency power source side toward the electrode side. In FIG. 4, the dielectric is not shown.

  In the example shown in FIG. 1, the conductor plate 38a has a symmetrical shape (isosceles triangle) with the direction perpendicular to the back surface of the electrode 12 as the axis (x-axis), but is not limited to this, and has an asymmetric shape. It may be. Note that the conductor plate 38a preferably has a symmetric shape from the viewpoint of suitably suppressing fine voltage fluctuations due to standing waves.

In the example illustrated in FIG. 1, the configuration includes one conductor plate 38 a, but the configuration is not limited thereto, and the configuration may include two or more conductor plates.
For example, the plasma generating apparatus 10c shown in FIG. 5 has two conductor plates 38c. In FIG. 5, the dielectric is not shown.
As shown in FIG. 5, the two conductor plates 38 c each have a maximum surface shape of an isosceles triangle, and the length of the base is half the width of the electrode 12. The two conductor plates 38c are arranged side by side in the width direction of the electrode 12. Moreover, the conducting wire 21 connected to a high frequency power supply (not shown) is connected to the vertex of each of the two conductor plates 38c.
In this manner, the high frequency power supply and the electrode may be connected by using a plurality of conductive plates whose width increases from the high frequency power supply side toward the electrode.
In the following description, when it is not necessary to distinguish the shape or the like of the conductor plate, the conductor plate 38 is collectively shown.

In the example shown in FIG. 1, the opposing surfaces (discharge surfaces) of the electrode and the counter electrode are flat surfaces, but the present invention is not limited to this, and the discharge surfaces of the electrode and the counter electrode are curved surfaces. There may be.
Even if the electrode has a curved shape, the conductor plate may have a curved shape.

  In the example shown in FIG. 3, the dielectric has a shape in which the thickness of the central portion in the width direction (y direction) of the conductor plate is thick and becomes thinner toward the end in the width direction. The dielectric constant is reduced as it goes from the central part to the end part in the width direction of the conductor plate, but is not limited thereto.

For example, as shown in FIG. 6, it is good also as a structure which laminates | stacks the several dielectric material from which the length of the width direction differs in the thickness direction.
In the example shown in FIG. 6, three dielectrics (24 a, 24 b, 24 c) are stacked between the conductor plate 38 and the ground conductor 18 in a direction perpendicular to the maximum surface of the conductor plate 38.
The three dielectrics have different widths and are laminated with the center in the width direction coinciding with the center of the conductor plate 38. Therefore, since three dielectrics are laminated between the conductor plate 38 and the ground conductor 18 at the center in the width direction, the thickness of the entire dielectric is increased. On the other hand, since only the dielectric 24a is disposed between the conductor plate 38 and the ground conductor 18 on the end side in the width direction, the thickness of the entire dielectric is reduced.
Thereby, it can be set as the structure which the dielectric constant by a dielectric material decreases as it goes to the edge part from the center part of the width direction of a conductor board.

Also, as shown in FIG. 7, a plurality of dielectrics having different relative dielectric constants may be arranged.
In the example shown in FIG. 7, three kinds of dielectrics (24 d, 24 e, 24 f) having different relative dielectric constants are arranged between the conductor plate 38 and the ground conductor 18 in the width direction of the conductor plate 38. The relative dielectric constant of the dielectric 24d disposed at the center in the width direction is ε _r1 , the relative dielectric constant of the dielectric 24e disposed on both sides of the dielectric 24d is ε _r2 , and is disposed on the end side of the dielectric 24e. that the dielectric relative permittivity of 24f epsilon _r3, when the relative dielectric constant of air and epsilon _0, satisfying the relation of _{ε r1> ε r2> ε r3} > ε 0. Accordingly, the dielectric constant due to the dielectric decreases in the direction from the center to the end in the width direction of the conductor plate.
As described above, a configuration in which a plurality of dielectrics having different relative dielectric constants are arranged may be configured such that the dielectric constant due to the dielectrics decreases from the center in the width direction of the conductor plate toward the end.

  Further, in the examples shown in FIGS. 3, 5, and 7, the dielectric constant due to the dielectric decreases as it goes from the center to the end in the width direction of the conductor plate by adjusting the thickness or relative dielectric constant of the dielectric. However, the present invention is not limited to this. For example, by changing the proportion of the dielectric in the space between the ground conductor and the conductor plate as a configuration in which the distance between the ground conductor and the conductor plate is varied according to the position in the width direction of the conductor plate, The dielectric constant due to the dielectric may be configured to decrease from the central portion to the end in the width direction of the conductor plate.

As an example, FIG. 8 shows a schematic front view of another example of the plasma generating apparatus of the present invention, and FIG. 9 shows a cross-sectional view taken along line BB of FIG.
In the example shown in FIGS. 8 and 9, the dielectric 24 and the five movable conductors (40a, 40b, 40c) are provided in one space between the conductor plate 38 and the ground conductor 18 from the conductor plate 38 side. Have. The five movable conductors are arranged in the width direction of the conductor plate 38. Each of the five movable conductors is provided with an adjustment mechanism 42 for adjusting the position of the movable conductor.
The five movable conductors are made of a conductive material and are grounded at the same potential as the ground conductor 18. That is, the movable conductor has a function electrically similar to that of the ground conductor 18.

The adjustment mechanism 42 is a member that supports the movable conductor so as to be movable in a direction (thickness direction) perpendicular to the maximum surface of the conductor plate 38. The configuration of the adjustment mechanism 42 is not limited, and a known mechanism can be used as appropriate.
In the example shown in FIG. 9, the adjustment mechanism 42 is a rod-shaped member, one end (base end) is fixed to the movable conductor, and the other end (tip) is the ground conductor 18. Is inserted through a through-hole formed in the outer surface of the ground conductor 18 and protrudes to the outside. The tip of the adjustment mechanism 42 is formed larger than the size of the through hole formed in the ground conductor 18.
Therefore, the adjustment mechanism 42 can move along the penetration direction of the through hole formed in the ground conductor 18, and by moving the adjustment mechanism 42, the movable conductor moves in a direction perpendicular to the maximum surface of the conductor plate 38. Can be made. Thereby, the ratio of the dielectric material 24 occupying the space between the conductor plate 38 and the movable conductor can be changed.

  As shown in FIG. 9, the movable conductor 40a at the center in the width direction is disposed at a position closest to the conductor plate 38, the two movable conductors 40c on both end sides are disposed at a position farthest from the conductor plate 38, and the movable conductor 40a is disposed. The movable conductor 40b between the movable conductor 40c and the movable conductor 40c is arranged at an intermediate position so that the proportion of the dielectric in the space between the movable conductor and the conductor plate 38 increases toward the center. Can do. Thereby, it can be set as the structure which the dielectric constant by a dielectric material decreases as it goes to the edge part from the center part of the width direction of a conductor board.

  Moreover, since the proportion of the dielectric in the space between the movable conductor and the conductor plate 38 can be changed, the phase can be adjusted by moving the movable conductor while confirming the uniformity of the plasma while the plasma is generated. can do.

Here, the height of the conductor plate 38 in the direction from the high frequency power supply 30 side to the electrode 12 is a, and the side of the conductor plate 38 other than the bottom side connected to the electrode 12 (hereinafter referred to as an oblique side, which is the same side in the example shown in FIG. 1). When the length is b (see FIG. 10) and the relative dielectric constant of the dielectric is ε _r , it is preferable that 0.7 ≦ (a × √ (ε _r )) / b ≦ 1.3 is satisfied.
As described above, when using a conductor plate whose width increases from the high-frequency power source side toward the electrode side, the length of the propagation path when high-frequency power propagates through the central portion of the conductor plate and the vicinity of the hypotenuse of the conductor plate The length of the propagation path when propagating is different. Therefore, the phase of the wave incident on the electrode differs depending on the position in the width direction. Therefore, a dielectric is disposed between the conductor plate and the ground conductor, and the dielectric constant due to the dielectric is configured to decrease from the central portion in the width direction of the conductor plate toward the end portion. The phase difference in the width direction of the incident wave is reduced by delaying the wave propagating through.
Here, a wave propagating through the center of the conductor plate (position of height a) and a wave propagating through the hypotenuse (position of length b) are considered. A dielectric is disposed at the center of the conductor plate, and its relative dielectric constant is ε _r . The velocity of the electromagnetic wave is v = 1 / √ (LC), and the capacitance C is proportional to the relative dielectric constant ε _r of the dielectric. Therefore, the wave propagating in the center is the same as the wave propagating in the hypotenuse. The arrival time is delayed by √ (ε _r ) times. Accordingly, if the difference between the length b of the hypotenuse and the length of √ (ε _r ) times the height a is reduced, the phase difference between the waves propagating through the respective sides is reduced, so that the influence of the standing wave is reduced.
From such a viewpoint, it is preferable that the height a, the length b of the hypotenuse, and the relative dielectric constant ε _r of the dielectric _satisfy 0.7 ≦ (a × √ (ε _r )) / b ≦ 1.3. Most preferably, the phase difference disappears (a × √ (ε _r )) / b = 1.
If the hypotenuse of the conductor plate is curved as shown in FIG. 4, an isosceles triangle included therein may be drawn and the length of the hypotenuse may be b. Further, when the conductor plate has an asymmetric shape, the length b of each of the two oblique sides preferably satisfies the above formula.

Further, considering not only the wave propagating through the center and the hypotenuse of the conductor plate, but also the wave propagating through any path in the conductor plate, the height in the direction from the high frequency power source to the electrode is a, the relative dielectric constant of the dielectric The rate is ε _r , the distance from the central axis toward the end in the width direction of the conductor plate is y, and the distance between the dielectric and the ground conductor at the distance y from the central axis is D, When the constant k is 0.8 ≦ k ≦ 1.2, the total thickness d (y) of the dielectric at the position y from the central axis is (see FIGS. 10 and 11).
d (y) = k × (a ² × (ε _r −1) −y ² ) × D / (a ² × (ε _r −1))
It is preferable to satisfy.
FIG. 12 schematically shows the shape of the dielectric that satisfies this d (y). As shown in FIG. 12, it becomes a curved shape, the phase difference in the width direction of the wave incident on the electrode can be further reduced, and the influence of the standing wave can be suppressed. In particular, when the shape of the dielectric is a shape that satisfies the case of k = 1 in the above formula d (y), each of the power supply points on the back surface of the electrode is propagated through a high-frequency path. The phase difference in the path is eliminated, and the standing wave can be most preferably suppressed.

Although not shown, the plasma generation apparatus 10 a may have a gas supply unit that supplies a processing gas for generating plasma between the electrode 12 and the counter electrode 14.
As the gas supply unit, all known gas supply means used in various plasma generation apparatuses can be used.
Further, as the processing gas, all known processing gases used in various plasma generation apparatuses can be used. For example, in the case where the plasma generation device is a device for forming a silicon nitride film by plasma CVD, the raw material for the silicon nitride film contains silane gas and ammonia gas, and if necessary, helium gas, neon gas, argon gas A gas containing various gases such as an inert gas such as krypton gas, xenon gas, and radon gas, nitrogen gas, hydrogen gas, and the like can be used as a processing gas.
For film formation other than the above, vaporized organosilane gas may be added to form a silica film, and methane or acetylene is added to form a carbon film with a carbon atom as a skeleton or a DLC (diamond-like carbon) film. May be. In the case of surface treatment or etching, fluorocarbon gas or oxygen gas can be added as a treatment gas.

  The plasma generation apparatus of the present invention has been described in detail above. However, the present invention is not limited to the above-described example, and various improvements and modifications may be made without departing from the scope of the present invention. Of course.

  Hereinafter, the present invention will be described in more detail based on examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the following examples.

[Example 1]
Evaluation was performed using a plasma generating apparatus as shown in FIG.
Each of the electrode 12 and the counter electrode 14 is an elongated flat plate electrode of width 1200 mm × depth 15 mm × thickness 5 mm, material: stainless steel. The distance between the electrode 12 and the counter electrode 14 was 0.5 mm. The counter electrode 14 was grounded.
The conductor plate 38a has an isosceles triangular shape on the maximum surface, a base width of 1200 mm, a height of 270 mm, and a thickness of 1 mm.

In order to electrically and electrically connect the conductor plate and the electrode, the bottom side of the conductor plate and the back surface of the electrode were joined by welding so that the connection location was a line segment. In order to obtain a high-frequency ground, the conductor plate was shielded by a copper plate enclosure (ground conductor). The distance between the ground conductor and the conductor plate (distance in the z direction) was 20 mm.
Further, a high frequency power source was connected to the apex of the conductor plate via a matching device.

In addition, a dielectric was disposed between the conductor plate and the ground conductor.
Epoxy resin was used as the dielectric. The relative dielectric constant is 5.6. As shown in FIG. 12, the shape of the dielectric is d (y) = k × (a ² × (ε _r −1) −y ² ) × D / (a ² × (ε _r −1)), k = 1 in shape. The thickness of the dielectric was continuously changed so that it was thickest at the center and thinnest at the hypotenuse. The thickness of the central part was 20 mm.

  Argon gas is introduced at a rate of 100 L / min between the electrode and the counter electrode of the plasma generator having such a configuration, and high-frequency power with a frequency of 27.12 MHz (500 W to 1500 W, standard 1200 W under atmospheric pressure) ) Was applied to generate plasma between the electrode and the counter electrode.

The voltage amplitude can be measured using an oscilloscope by pressing the tip of the high-voltage probe (Tektronix P6015A) against the electrically exposed electrode (back) while the plasma is ignited. it can. The voltage distribution in the width direction can be observed by changing the position (y: 0 to 1200 mm) on the electrode to which the high voltage probe is attached. The voltage uniformity is examined by acquiring this distribution.
While measuring by moving the probe in the width direction, the voltage distribution in the width direction was measured. After obtaining the maximum and minimum voltages from the measured voltage distribution, a fluctuation ratio (expressed in%) defined by {(maximum voltage) − (minimum voltage)} × 100 / (maximum voltage) was calculated. It can be concluded that the smaller the variation ratio, the better the plasma generation with respect to uniformity.
FIG. 13 shows the measurement result of the voltage distribution.
The fluctuation ratio was calculated to be 8%.

[Comparative Example 1]
As in the plasma generating apparatus 100a shown in FIG. 15, a configuration in which three conductive wires 122 are used instead of the conductor plate and feed points are provided for three points on the electrode 112, and a dielectric is not disposed. The evaluation was performed using the same plasma generator as in Example 1 except that.
A copper plate having a width of 15 mm was used as the conducting wire 122.
The positions of the feeding points were the both ends and the center in the width direction of the electrode 11. Further, the point from which the conducting wire 121 output from the matching circuit 132 branches to the central feeding point was linearly connected by a 270 mm copper plate (conducting wire 122). Moreover, the conducting wire 122 connected to the feeding point of both ends from the point where the conducting wire 121 branches was also connected linearly.
FIG. 14 shows the measurement result of the voltage distribution.
The fluctuation ratio was calculated to be 45%.

[Comparative Example 2]
Evaluation was performed using a plasma generation apparatus similar to that of Comparative Example 1 except that a feeding point was provided for five points on the electrode 112 as in the plasma generation apparatus 100b shown in FIG.
The position of the feeding point was the both ends and the center of the electrode 11 in the width direction, and an intermediate position between them. The distance between each feeding point was set at equal intervals (300 mm).
FIG. 14 shows the measurement result of the voltage distribution.
The fluctuation ratio was calculated to be 52%.

[Comparative Example 3]
A configuration in which the space between the conductor 122 and the ground conductor 118 is closed with a dielectric for the three conductors 122 connected to the central and intermediate feed points as in the plasma generating apparatus 100c shown in FIG. Evaluation was performed using the same plasma generating apparatus as in Comparative Example 2 except that.
As the dielectric, alumina (relative dielectric constant 9.5) was used.
In addition, power is supplied from a high-frequency power source, the position dependency of the voltage amplitude difference is measured in a state where the plasma is ignited, and the fluctuation ratio is recorded. The number of dielectrics used, that is, the thickness is increased and / or decreased in each conductor 122 to find the optimum point while changing the dielectric constant of the path, and the thickness of the dielectric that minimizes the voltage width direction distribution. Fixed.
FIG. 14 shows the measurement result of the voltage distribution.
The fluctuation ratio was calculated to be 25%.

  From FIG. 13 and FIG. 14 and the calculation result of the fluctuation ratio, the fluctuation ratio of the embodiment of the present invention is smaller than that of the comparative example, so that fine voltage fluctuations due to standing waves can be reduced, and the length of the propagation path is different. It can be seen that the wave phase difference due to can be reduced.

Further, the configuration of Comparative Example 3 is a configuration intended for the configuration of multi-point power feeding + phase difference adjustment performed in the prior art, and by such extension of the prior art, a better result than this will be obtained. Then, it can be seen from the comparison between Comparative Example 1 and Comparative Example 2 that it is necessary to further supply power at multiple points. Furthermore, it can be seen from the comparison between Comparative Example 2 and Comparative Example 3 that it is necessary to adjust the dielectric by disposing a dielectric on each of the conducting wires that are multi-point fed. Therefore, it becomes clear that it becomes a complicated mechanism.
On the other hand, it can be seen that the present invention can suppress standing waves at a high level with a simple configuration.
From the above, the effects of the present invention are clear.

10a to 10c, 100a, 100b Plasma generator 12, 112 Electrode 14, 114 Counter electrode 18, 118 Ground conductor (external conductor)
21, 121 Conductor 24, 24a-24f Dielectric 30, 130 High frequency power supply 32, 132 Matching device 36, 136 Coaxial cable 38, 38a-38c Conductor plate 39 Feeding point 40a-40c Movable conductor 42a-42c Adjusting mechanism 122 Conductor

Claims (4)

electrode,
A counter electrode arranged to face the main surface of the electrode,
A high frequency power source for supplying high frequency power to the electrode to excite plasma between the electrode and the counter electrode;
A conductor plate connected to the electrode from the high-frequency power source;
A grounded ground conductor disposed over the conductor plate; and
Having a dielectric disposed at least in part between the conductor plate and the ground conductor;
The width of the conductor plate increases from the high-frequency power source side toward the electrode side,
The plasma generating apparatus, wherein a dielectric constant of the dielectric decreases as it goes from a central portion to an end portion in the width direction of the conductor plate. When the length of the oblique side of the conductor plate is b, the height in the direction from the high-frequency power source toward the electrode is a, and the relative dielectric constant of the dielectric is ε _r , 0.7 ≦ (a × √ (ε _r )) / B ≦ 1.3. The plasma generating apparatus according to claim 1, wherein: The height in the direction from the high-frequency power source to the electrode is a, the relative dielectric constant of the dielectric is ε _r , and the distance from the central axis to the end in the width direction of the conductor plate is y, When the distance between the dielectric and the ground conductor at a distance y from the axis is D and the constant k is 0.8 ≦ k ≦ 1.2, the distance y from the central axis is The total thickness d (y) of the dielectric is
d (y) = k × (a ² × (ε _r −1) −y ² ) × D / (a ² × (ε _r −1))
The plasma generation apparatus according to claim 1 or 2, wherein:   3. The plasma generation apparatus according to claim 1, wherein the dielectric is disposed so that a ratio of the dielectric occupying a space between the conductor plate and the ground conductor adjacent to the conductor plate can be changed. .