Inductive Plasma Source Coupling Efficiency via Thin Windows
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Solution Overview
Problem
Inductive coupled plasma (ICP) processing methods face challenges with low power transfer efficiency, plasma nonuniformity, and difficulties in maintaining low power and low plasma density operations due to weak coupling between the applicator and plasma, as well as inefficient feed gas distribution.
Innovation Solution
The use of thin dielectric windows and magnetic flux concentrators within the processing chamber to enhance coupling efficiency, with inductive plasma applicators positioned close to the plasma to improve power transfer and uniformity, and strategically placed feed gas holes for uniform gas distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick dielectric window is used to withstand atmospheric pressure, then mechanical strength is improved, but the distance between the applicator and plasma increases, reducing coupling efficiency
Solution Approach 1:
The patent divides the chamber wall into multiple sections with thin dielectric windows separated by non-dielectric structural supports. Each thin window segment is mechanically supported independently, allowing the use of thin windows (reducing RF power loss) while maintaining overall structural strength to withstand atmospheric pressure through distributed support structures.
2Stability of the object's composition
If the applicator is positioned far from the plasma, then mechanical stability is improved, but coupling efficiency decreases, requiring higher applicator voltage
Solution Approach 1:
The patent uses thin dielectric windows as flexible barriers that allow the applicator to be positioned very close to the plasma (within millimeters) while maintaining mechanical separation. The thin dielectric film provides sufficient electrical isolation and mechanical stability while enabling tight coupling between the applicator and plasma, eliminating the need for large safety distances.
3Power
If high applicator voltage is used to compensate for weak coupling, then power transfer to plasma is maintained, but RF power loss in the applicator increases
Solution Approach 1:
The patent uses thin dielectric windows that enable excessive coupling (applicator positioned extremely close to plasma), creating such strong coupling that the system operates efficiently at lower applicator voltages. This partial action approach uses just enough coupling to achieve high efficiency without the excessive voltage requirements that would cause high RF power losses.
4Manufacturing precision
If a flat dielectric window is used, then plasma uniformity is improved, but the window thickness must be increased to withstand atmospheric pressure
Solution Approach 1:
The patent segments the chamber wall into multiple thin dielectric window sections separated by structural supports. Each segment remains thin to maintain plasma uniformity, while the distributed support structure collectively withstands atmospheric pressure. This segmentation allows flat window geometry for uniform plasma while avoiding the need for thick windows.
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
This approach achieves high power transfer efficiency, improved plasma uniformity, and stable operation at low power and low plasma density, reducing costs associated with excess power supply capacity and enhancing processing efficiency.
Implementation Method 1
maintaining a substantially inductive plasma wholly within the chamber with magnetic flux produced by energizing at least one inductive plasma applicator outside of the processing chamber with radiofrequency power
Implementation Method 2
At least one inductive coupling element among the one or more inductive coupling elements comprises a magnetic flux concentrator operable to reduce the magnetic path resistance for magnetic flux lines in the inductive coupling element
Implementation Method 3
Each inductive coupling element also can emit magnetic flux into the chamber interior and receive the magnetic flux returning from the chamber interior through the associated one thin window
Data Source
AI summary
A method and apparatus are provided for processing a substrate with a radiofrequency inductive plasma in the manufacture of a device. The inductive plasma is maintained with an inductive plasma applicator having one or more inductive coupling elements. There are thin windows between the inductive coupling elements and the interior of the processing chamber. Various embodiments have magnetic flux concentrators in the inductive coupling element and feed gas holes interspersed among the inductive coupling elements. The thin windows, magnetic flux concentrators, and interspersed feed gas holes are useful to effectuate uniform processing, high power transfer efficiency, and a high degree of coupling between the applicator and plasma. In some embodiments, capacitive current is suppressed using balanced voltage to power an inductive coupling element.