Transformer Isolator RF Shield Radial Segments Plasma Power Transfer
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Solution Overview
Problem
Traditional RF filters in plasma processing systems suffer from unit-to-unit variability and parasitic resonances, leading to repeatability issues and inefficiencies in power transfer to substrate heaters, causing loss of etch-rate and potential damage to AC circuitry.
Innovation Solution
An isolation transformer with a unique shielding configuration, featuring a primary and secondary ferrite structure with radial segments and slits, optimized for efficient magnetic power transfer while blocking electrostatic currents, thereby reducing eddy current dissipation and enhancing power delivery to substrate heaters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional LC tank filters are used to block electrostatic currents, then RF power isolation is improved, but unit-to-unit variability and parasitic resonances cause repeatability issues
Solution Approach 1:
The shield is segmented into multiple radial segments instead of being a continuous structure. This segmentation eliminates parasitic resonances that occur in traditional continuous shields while maintaining effective RF isolation. Each radial segment acts independently, preventing the formation of resonant modes that would cause variability between units.
Solution Approach 2:
Instead of using traditional LC tank circuits with coils and capacitors to achieve RF isolation, the invention inverts the approach by using a geometrically-configured radial segment shield structure. This inverted methodology achieves the same isolation function through structural geometry rather than resonant circuit elements, eliminating unit-to-unit variability.
2Loss of energy
If RF filters are added to block electrostatic currents, then power transfer efficiency to heaters is improved, but device complexity increases
Solution Approach 1:
The shield structure is merged with the existing transformer assembly, eliminating the need for separate external filters. The radial segments are integrated directly into the transformer housing, combining the shielding function with the structural support function, thereby reducing overall device complexity while maintaining power transfer efficiency.
Solution Approach 2:
The radial segment shield acts as an intermediary structure between the primary and secondary windings, providing RF isolation without requiring additional filter components. This intermediary structure achieves the blocking function through its geometric configuration rather than through separate filter elements.
3Temperature
If AC circuitry is used to power heaters, then temperature control is achieved, but RF power is inadvertently drawn from plasma causing etch-rate loss
Solution Approach 1:
The harmful RF power coupling is extracted and blocked by the radial segment shield structure. The shield selectively removes the unwanted RF interference from the plasma while allowing the necessary AC power to pass through to the heaters, thereby protecting etch-rate from degradation.
4Reliability
If shields are added to block RF power, then isolation is improved, but magnetic power transfer efficiency may deteriorate
Solution Approach 1:
The shield structure exhibits local quality variations through its radial segmentation. The gaps between segments are strategically positioned to allow magnetic flux penetration while the solid radial portions provide RF blocking. This local differentiation enables simultaneous achievement of RF isolation and magnetic power transfer efficiency.
Solution Approach 2:
The radial segments are nested within the transformer structure, with the shield segments positioned inside the magnetic field path. This nested configuration allows the shield to block RF power while the magnetic field passes through the gaps between segments, maintaining power transfer efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively isolates RF power from returning to the primary circuitry, maintaining efficient magnetic power transfer and reducing capacitive coupling, thus improving etch uniformity and preventing damage to AC circuitry.
Implementation Method 1
A primary shield is disposed over the primary ferrite and the primary coil. The primary shield includes a first plurality of radial segments that extend from a primary center region to outside a periphery of the primary ferrite.
Implementation Method 2
A primary ferrite is disposed over the primary base plate. The primary ferrite has a primary circular channel. A primary coil is wound within the primary circular channel.
Implementation Method 3
Each of the plurality of radial segments includes a plurality of slits
Data Source
AI summary
An apparatus for a transformer isolator used for transferring power to an element of a substrate support used in a plasma chamber is provided. A primary of the transformer isolator includes a primary base plate configured to electrically couple to ground. A primary ferrite disposed over the primary base plate, and the primary ferrite has a primary circular channel. A primary coil is wound within the primary circular channel. A primary shield is disposed over the primary ferrite and the primary coil. The primary shield includes a first plurality of radial segments that extend from a primary center region to outside a periphery of the primary ferrite. An extended region of the primary shield has a curved section to connect the primary shield with the primary base plate. In one example, the secondary of the transformer isolator has similar construction as the primary and are used together as part of the transformer isolator.