Dielectric Window Convex Layout for Uniform VHF Plasma Processing
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Solution Overview
Problem
Plasma distribution in plasma processing using VHF waves is often biased in the circumferential direction due to varying electromagnetic wave intensity and pressure, leading to non-uniform processing results.
Innovation Solution
A plasma processing apparatus with a dielectric window featuring multiple convex portions arranged at regular intervals, where each convex portion has a circumferential width of ⅛ to ⅜ of the wavelength of VHF waves, concentrates electric fields and suppresses circumferential bias, ensuring uniform plasma distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a flat dielectric window is used to transmit VHF electromagnetic waves, then the structure is simple and easy to manufacture, but the plasma distribution becomes biased in the circumferential direction leading to non-uniform processing
Solution Approach 1:
The dielectric window features convex portions with different shapes and positions in different regions. Specifically, the circumferential width of convex portions varies with their position along the circumferential direction, and the height of convex portions also varies. This local variation in geometry creates non-uniform electric field distribution that compensates for the inherent circumferential bias in VHF plasma generation, achieving uniform plasma distribution across the processing area.
2Productivity
If microwaves are used for plasma generation, then plasma can be generated effectively, but the apparatus size becomes large and cannot be miniaturized
Solution Approach 1:
The patent changes the frequency parameter of electromagnetic waves from microwave frequency to VHF frequency. This parameter change allows for smaller apparatus dimensions since VHF wavelengths are shorter than microwave wavelengths. The convex portions on the dielectric window are specifically designed with dimensions (circumferential width of 1/8 to 3/8 of wavelength) optimized for VHF frequencies, enabling effective plasma generation at the lower frequency while achieving apparatus miniaturization.
3Manufacturing precision
If the circumferential width of convex portions is not optimized, then manufacturing is easier, but plasma distribution uniformity deteriorates
Solution Approach 1:
The patent establishes specific parameter ranges for the convex portions: the circumferential width should be 1/8 to 3/8 of the electromagnetic wave wavelength. This parameter optimization ensures that the convex portions effectively concentrate electric fields to generate uniform plasma distribution. The precise dimensional control is justified by the significant improvement in plasma uniformity, making the manufacturing complexity acceptable for achieving the desired processing quality.
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 achieves uniform film thickness and processing results in the circumferential direction, even with varying plasma generation conditions, and allows for miniaturization of the processing apparatus by using VHF waves instead of microwaves.
Implementation Method 1
a dielectric window configured to transmit the electromagnetic waves introduced through the waveguide part to a plasma processing space
Implementation Method 2
multiple convex portions, which protrude toward the stage and are arranged on the stage side along a circumferential direction at regular intervals... concentrates electric fields and suppresses circumferential bias
Implementation Method 3
a waveguide part configured to introduce plasma-generating electromagnetic waves in a VHF band into the plasma processing apparatus... generate plasma inside the vacuum chamber
Data Source
AI summary
A plasma processing apparatus for processing a workpiece with plasma includes a stage configured to place thereon the workpiece, a waveguide part configured to introduce plasma-generating electromagnetic waves in a VHF band into the plasma processing apparatus, and a dielectric window configured to transmit the electromagnetic waves introduced through the waveguide part to a plasma processing space formed on a workpiece placement side of the stage. The dielectric window is an annular member disposed so as to face a plasma processing space side of the stage and includes multiple convex portions, which protrude toward the stage and are arranged on the stage side along a circumferential direction at regular intervals. The convex portions each has a circumferential width of ⅛ to ⅜ of the wavelength of the electromagnetic waves inside the dielectric window.