Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Plasma generating
Reexamination Certificate
2001-03-29
2002-12-17
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Plasma generating
C315S111210, C315S344000, C118S7230IR, C118S7230ER
Reexamination Certificate
active
06495963
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to inductive coil assemblies for plasma processing apparatus.
As will be discussed in more detail below, there are currently many coil configurations for generating an inductively coupled plasma in a vacuum chamber for processing purposes. In at least most configurations, there can be capacitive coupling between the coil configuration and the plasma and the level of this capacitive coupling is related to the potential difference dropped across the coil configuration. Whilst such capacitive coupling can be beneficial in certain arrangements, there are also significant disadvantages and in particular it can lead to uncontrolled and undesired etching of surfaces within the chamber.
SUMMARY OF THE INVENTION
From one aspect the invention consisting an inductive coil assembly for plasma processing apparatus including a coil and an external screen characterised in that the coil is constituted by a plurality of coil portions and in that the assembly includes respective connecting means for connecting each portion in parallel with the others and to an RF source, the connecting means being formed such that the current flowing in any part of the coil other than a segment of a portion is balanced by current flowing in an opposite sense in an adjacent part.
Each coil assembly may be constituted by a plurality of adjacent segments which together define the inductive coupling portion of a cylindrical coil. That is to say each segment may be an arc. Conveniently the segments may be in the form of strips such that the coil is effectively in the form of a cylinder or frustocone. In any of these cases the connecting means may include a pair of rings and the portions may bridge between the rings.
In an alternative arrangement each segment may be constituted on a loop so that segments together form an array corresponding to a generally planar, domed or curved coil. The array may be constituted so that the segments are those parts of the portions which are unbalanced and thus produce net field. These will include those which lie on the periphery of the array.
The connecting means may include co-axial connections and/or rings. The latter may constitute a screen.
A respective capacitor may be connected across each portion so that the capacitors are connected in parallel. An advantage of the distribution of these capacitors is that it reduces current crowding by distributing current more evenly throughout the RF structure.
From another aspect the invention consists in an inductive coil assembly for plasma processing apparatus including a coil characterised in that the coil is constituted by a plurality of coil segments connected in series to form a loop, each coil segment being separated from its neighbour by a series connected capacitor, and in that the assembly includes means for supplying RF power to the loop.
The power supply means may be connected across one of the capacitors or, alternatively, it may include a coil for inducing RF power in the loop, in which case the mid-point of each segment is preferably earthed.
The segments may be equal in length and the capacitor values may be such that they resonate with the segments so that the reactive voltage in each segment is cancelled out.
Although the invention has been defined above it is to be understood it includes any inventive combination of the features set out above or in the following description.
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Philogene Haissa
Trikon Holdings Limited
Volentine & Francos, PLLC
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