POWER DELIVERY SYSTEMS AND MANUFACTURING EQUIPMENT INCLUDING A VARIABLE VACUUM CAPACITOR

Abstract

A variable vacuum capacitor includes two pairs of electrodes ganged together in series such that no moving parts are required to connect electrically to any static pans. Two sets, or gangs, of movable electrodes are connected mechanically and electrically together such that they move together and such that they require no electrical connection to any other part of the device. The ganged arrangement means that the device can be constructed with a smaller diameter, but without significantly increasing the overall length of the device. The variable vacuum capacitor may be a component of e.g., a power delivery system for a plasma process, a power delivery system for surface treatment, semi-conductor manufacturing equipment, photovoltaic manufacturing equipment, and flat panel manufacturing equipment.

Claims

1. A power delivery system for a plasma process, comprising: at least one variable vacuum capacitor, the variable vacuum capacitor comprising a vacuum enclosure, a first variable electrode assembly comprising one or more first static electrodes and one or more first mobile electrodes, a second variable electrode assembly comprising one or more second static electrodes and one or more second mobile electrodes, a first electrical connection terminal for providing an electrical connection to the one or more first static capacitor electrodes, a second electrical connection terminal for providing an electrical connection to the one or more second static capacitor electrodes, displacement means for displacing the first and/or second mobile electrodes relative to the first and/or second static electrodes respectively, along an axis of the vacuum capacitor, wherein, in the variable vacuum capacitor, the first and second electrode assemblies are ganged along the axis such that the first mobile electrode assembly is offset along the axis by a gang offset distance from the second electrode assembly, and the variable vacuum capacitor comprises mobile electrode linkage means for providing a kinematic linkage between the one or more first mobile electrodes at a first position along the axis and the one or more second mobile electrodes at a second position along the axis, such that a first displacement along the axis of the one or more first mobile electrodes results in a second displacement along the axis of the one or more second mobile electrodes.

2. A power delivery system for surface treatment, comprising: at least one variable vacuum capacitor, the variable vacuum capacitor comprising a vacuum enclosure, a first variable electrode assembly comprising one or more first static electrodes and one or more first mobile electrodes, a second variable electrode assembly comprising one or more second static electrodes and one or more second mobile electrodes, a first electrical connection terminal for providing an electrical connection to the one or more first static capacitor electrodes, a second electrical connection terminal for providing an electrical connection to the one or more second static capacitor electrodes, displacement means for displacing the first and/or second mobile electrodes relative to the first and/or second static electrodes respectively, along an axis of the vacuum capacitor, wherein, in the variable vacuum capacitor, the first and second electrode assemblies are ganged along the axis such that the first mobile electrode assembly is offset along the axis by a gang offset distance from the second electrode assembly, and the variable vacuum capacitor comprises mobile electrode linkage means for providing a kinematic linkage between the one or more first mobile electrodes at a first position along the axis and the one or more second mobile electrodes at a second position along the axis, such that a first displacement along the axis of the one or more first mobile electrodes results in a second displacement along the axis of the one or more second mobile electrodes.

3. Semi-conductor manufacturing equipment, comprising: at least one variable vacuum capacitor, the variable vacuum capacitor comprising a vacuum enclosure, a first variable electrode assembly comprising one or more first static electrodes and one or more first mobile electrodes, a second variable electrode assembly comprising one or more second static electrodes and one Or more second mobile electrodes, a first electrical connection terminal for providing an electrical connection to the one or more first static capacitor electrodes, a second electrical connection terminal for providing an electrical connection to the one or more second static capacitor electrodes, displacement means for displacing the first and/or second mobile electrodes relative to the first and/or second static electrodes respectively, along an axis of the vacuum capacitor, wherein, in the variable vacuum capacitor, the first and second electrode assemblies are ganged along the axis such that the first mobile electrode assembly is offset along the axis by a gang offset distance from the second electrode assembly, and the variable vacuum capacitor comprises mobile electrode linkage means for providing a kinematic linkage between the one or more first mobile electrodes at a first position along the axis and the one or more second mobile electrodes at a second position along the axis, such that a first displacement along the axis of the one or more first mobile electrodes results in a second displacement along, the axis of the one or more second mobile electrodes.

4. Photovoltaic manufacturing equipment, comprising: at least one variable vacuum capacitor, the variable vacuum capacitor comprising a vacuum enclosure, a first variable electrode assembly comprising one or more first static electrodes and one or more first mobile electrodes, a second variable electrode assembly comprising one or more second static electrodes and one or more second mobile electrodes, a first electrical connection terminal for providing an electrical connection to the one or more first static capacitor electrodes, a second electrical connection terminal for providing an electrical connection to the one or more second static capacitor electrodes, displacement means for displacing the first and/or second mobile electrodes relative to the first and/or second static electrodes respectively, along an axis of the vacuum capacitor, wherein, in the variable vacuum capacitor, the first and second electrode assemblies are ganged along the axis such that the first mobile electrode assembly is offset along the axis by a gang offset distance from the second electrode assembly, and the variable vacuum capacitor comprises mobile electrode linkage means for providing a kinematic linkage between the one or more first mobile electrodes at a first position along the axis and the one or more second mobile electrodes at a second position along the axis, such that a first displacement along the axis of the one or more first mobile electrodes results in a second displacement along the axis of the one or more second mobile electrodes.

5. Flat-panel manufacturing equipment, comprising: at least one variable vacuum capacitor, the variable vacuum capacitor comprising a vacuum enclosure, a first variable electrode assembly comprising one or more first static electrodes and one or more first mobile electrodes, a second variable electrode assembly comprising one or more second static electrodes and one or more second mobile electrodes, a first electrical connection terminal for providing an electrical, connection to the one or more first static capacitor electrodes, a second electrical connection terminal for providing an electrical connection to the one or more second static capacitor electrodes, displacement means for displacing the first and/or second mobile electrodes relative to the first and/or second static electrodes respectively, along an axis of the vacuum capacitor, wherein, in the variable vacuum capacitor, the first and second electrode assemblies are ganged along the axis such that the first mobile electrode assembly is offset along the axis by a gang offset distance from the second electrode assembly, and the variable vacuum capacitor comprises mobile electrode linkage means for providing a kinematic linkage between the one or more first mobile electrodes at a first position along the axis and the one or more second mobile electrodes at a second position along the axis, such that a first displacement along the axis of the one or more first mobile electrodes results in a second displacement along the axis of the one or more second mobile electrodes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The invention will now be described in detail, with reference to the accompanying drawings, in which:

[0048] FIG. 1 shows in schematic, sectional view, a simple prior art variable vacuum capacitor having a single pair of electrodes.

[0049] FIG. 2 shows in schematic, sectional view, a prior an variable vacuum capacitor have two sets of electrodes arranged electrically in series, and mechanically in parallel.

[0050] FIG. 3 shows in schematic, sectional view, an example of a variable vacuum capacitor according to an aspect of the invention, having two sets of electrodes arranged electrically and mechanically in series.

[0051] FIG. 4 schematically shows a power delivery system according to aspects of the present invention in equipment according to aspects of the present invention including tuning circuits having variable vacuum capacitors according to aspects of the present invention.

[0052] The figures are provided for illustrative purposes only, and should not be construed as limiting the scope of the claimed patent protection. Where the same references have been used in different drawings, they are intended to refer to similar or corresponding features. However, the use of different references does not necessarily indicate that the features to which they refer are different.

DETAILED DESCRIPTION

[0053] FIG. 1 illustrates the configuration of a simple variable vacuum capacitor as known in the prior art. Such a vacuum capacitor typically consists of or comprises two conducting high voltage terminals, 24 and 9, attached to an insulating cylindrical vacuum enclosure wall, 26, in a vacuum-tight manner. Increasing the overlap area of electrodes, 7 and 8, and/or decreasing their separation, increases the capacitance value of the device. The electrodes 7 and 8 are conductively attached to the terminals 24 and 9 respectively. In order to vary the capacitance of the variable vacuum capacitor device, one electrode, 7, is moved with respect to the other. This is typically achieved by means of an expansion joint (bellows, 5) and a drive system, 16, 12 whose motion is controlled by an electrical motor, 1, such as a stepper motor.

[0054] As mentioned above, the bellows 5 have a triple function: while transmitting the movement to the movable electrode, 7, they must also carry the electrical high-frequency current from the terminal, 24, to the movable electrode, 7, while also separating the vacuum from the drive system, which is at atmospheric pressure. This limits the choice of material for the bellows, 5, to very few options, as it must be optimized simultaneously for electrical characteristics and for mechanical characteristics. Even with a good choice of material, the long path of the electrical current along the bellows, 5, (high-frequency currents are forced to flow along the surface of conductors, a phenomenon known as skin effect) can result in considerable electrical losses inside a very critical part of the device, thereby generating undesired heat and an additional parasitic electrical resistance to the capacitive device. Such elevated temperatures and thermal cycling will reduce the total number of cycles the expansion joint, 5, will work, thereby reducing the operating lifetime of the variable vacuum capacitor.

[0055] FIG. 2 shows a schematic representation of a series electrode arrangement known in the prior art (eg US2005052820 A1).

[0056] Two concentric electrode sets, 7, 8 and 17, 18 are arranged, one outside the other, in the same plane, with a common support element 22 supporting all the mobile electrodes 7, 17. To increase the capacitance, the height and number of the electrode surfaces must be increased, which means increasing the dimensions of the device. Alternatively, the spacing between the electrodes can be decreased, which leads to a lower maximum operating voltage of the device.

[0057] Connections to the variable vacuum capacitor are made at the end surfaces 13 and 14, which are connected internally to the static and mobile electrodes 18 and 17 respectively. The bellows, 5, are at least partially made of an insulating material such that no current can flow between the mobile electrodes 22, 17 and the upper terminal 14.

[0058] FIG. 3 shows an example of a variable vacuum capacitor according to an aspect of the invention. The required capacitance is generated by means of two electrode assemblies, 17, 18, 21, 23 and 7, 8, 11, 13. Each electrode assembly comprises one or more movable 7, 17 and one or more fixed 8, 18 electrodes. Each set of electrodes may be for example be constructed as one or more concentric cylinders or as a spiral having one or more turns.

[0059] One set of static electrodes, 18, is shown supported by a support element, 23, secured to the wall 4 of the vacuum enclosure. The other set of static electrodes, 8, is shown supported by the end cap 13 of the vacuum capacitor and the end terminal 9.

[0060] One mobile sets of electrodes 17 is shown supported by electrode support 21, which is in turn supported by insulator 2 and insulating bellows 5 and motor drive 12, 16. Electrode support 21 is mechanically and electrically connected by a connecting means, 10, denoted by dashed line, to the electrode support 11 of the lower mobile electrodes 7. In the simple case, the connecting means may be a simple, rigid element such as a cylinder of copper. In this case, the wall of the cylinder is provided with openings so as to allow the cylinder 10 to move up and down parallel to the longitudinal axis A of the device without interfering with the electrode support 23, which has one or more arms or other support structures for securing to the wall 4 of the vacuum enclosure.

[0061] The series connection of the two electrode assemblies means that the current which flows to and from the terminals is obliged to follow a path which does not include any moving parts such as bellows. Moreover, instead of being at opposite ends of the variable vacuum capacitor, the two high voltage terminals of the device can be placed at or towards one end of the device, for example in a region at a mid-point along the length of the device at the lateral cylinder periphery.

[0062] Siting the terminal 4 at a mid-way point on the length of the vacuum enclosure also means that the current path from the terminal to the static electrodes 18 is short and direct, which in turn minimises unwanted EMC emissions and thermal dissipation.

[0063] In this way, the variable vacuum capacitor has an end portion 14 to which the motor assembly 1 can be mounted, at least a portion which is essentially free of the influence of the high voltages present at either end of a conventional variable vacuum capacitor.

[0064] FIG. 3 shows the motor mounting terminal 14 separated from the high voltage terminals 4 by an insulating vacuum enclosure part, 6. Because the bellows do not carry current, they also do not need to be electrically conducting, and therefore motor mounting terminal 14 is also insulated from the electrodes 7. Alternatively if one still uses a conducting bellows 5, then an insulating part 2 at either end of the bellows 5 would insulate the motor terminal 14 and motor 1 from the electrodes 7. Because this insulating part is in vacuum, it does not need to be as large as the motor-insulating part 19 used outside the vacuum in prior art (see FIGS. 1 and 2).

[0065] The advantage provided by being able to mount the motor directly on the vacuum capacitor enclosure makes the motorized variable vacuum capacitor of the present invention more compact and/or frees space to be filled with electrodes inside the vacuum. This is turn results in higher achievable capacitance values and higher achievable maximum operating voltages.

[0066] In FIG. 2, electrode pairs are shown mounted in series, co-axially, each electrode of each pair mounted one above the other along a single axis corresponding to the movement axis. A (there are no inner or outer electrodes, as there are in the device shown in FIG. 2), resulting in a small diameter (perpendicular to the movement axis) similar to the devices of prior art not using a serial geometry (such as those of FIG. 1) and resulting in a smaller diameter as the devices of prior art using a serial geometry (such as those of FIG. 2).

[0067] At the same time, the voltage capability of a serial geometry is increased between the two high voltage terminals, 4 and 9, because the total voltage splits between the different pairs of electrodes in series. For example, in the example embodiment shown in FIG. 3, the voltage between the conducting surfaces 4 and 17 and the voltage difference between the conductive surfaces 7 and 9 are half the voltage difference applied across the terminals 4 and 9 of the variable vacuum capacitor. This voltage splitting, which is a consequence of mounting electrodes in series, is advantageous because it permits smaller electrode separation without risking voltage breakdowns in the vacuum; and thanks to the smaller electrode separation achievable, the capacitance value can be significantly increased.

[0068] In the example shown in FIG. 3, both movable electrodes 7 and 17 are shown connected by a conducting piece (10), preferably made of a good electrical conductor and preferably structured as a rigid tube-shaped part having a diameter similar but bigger than the outermost surface of the fixed electrode, therefore generating an additional capacitative contribution.

[0069] Note that only two pairs of electrodes are depicted in FIG. 3, but it will be understood that the invention also covers the use of multiple pairs of electrodes.

[0070] FIG. 4 schematically shows components of a power delivery system of the present invention in equipment that can be used for a variety of purposes including a plasma process, surface treatment, semi-conductor manufacturing, photovoltaic manufacturing, and flat panel manufacturing. In such equipment, a chamber 121 can be provided with a target 123 on a lid of the chamber. A pedestal 125 can also be disposed in the chamber 121. A first RF generator 127 may be coupled to the target 123 through a first impedance matching network 129 that includes a tuning circuit 131 that includes adjustable circuit elements such as one or more variable vacuum capacitors. A second RF generator 133 may be coupled to the pedestal 125 through a second impedance matching network 135 that includes a tuning circuit 137 that includes adjustable circuit elements such as one or more variable vacuum capacitors. It is understood that only one of the above cited generators 129, 133 may be required in some applications while the other generator may be replaced by a DC bias power supply, or a simple grounded connection depending on the specific application. A sample S to be processed in the chamber 121 may be processed via known plasma process or other surface treatment techniques using high frequency electric power, for e.g., coating, etching, ashing, cleaning processes in semi-conductor manufacturing, photovoltaic manufacturing, and fiat panel manufacturing. U.S. Pat. No. 8,491,759 discloses embodiments of such equipment and is incorporated by reference.

[0071] In the present application, the use of terms such as including is open-ended and is intended to have the same meaning as terms such as comprising and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as can or may is intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or arts are presently considered to be essential, they are identified as such.

[0072] While this invention has been illustrated and described in accordance with a preferred embodiment, it is recognized that variations and changes may be made therein without departing from the invention as set firth in the claims.