Retractable Bellows Sealing for Stable RF Plasma Etching
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Solution Overview
Problem
Stainless steel bellows used in plasma processing devices experience instability in radio-frequency environments due to changing capacitance and inductance, leading to uncertain resonances and thermal energy loss, affecting the etching rate stability.
Innovation Solution
A retractable sealing part with a bellows assembly and sleeve assembly, including metal sleeves and isolation rings, is designed to shield radio-frequency coupling, maintaining vacuum isolation and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stainless steel bellows are used for vacuum isolation and extension/retraction, then mechanical strength and extension stroke are improved, but radio-frequency circuit stability deteriorates due to changing capacitance and inductance
Solution Approach 1:
The bellows structure is segmented into multiple stainless steel foil layers (e.g., 3-5 layers) stacked together. This segmentation maintains mechanical strength while reducing the impact of capacitance and inductance changes on radio-frequency circuit stability by distributing the electrical properties across multiple thin layers.
Solution Approach 2:
A radio-frequency shielding structure (such as a conductive shield or grounding screen) is introduced as an intermediary between the stainless steel bellows and the radio-frequency circuit. This shield blocks the harmful electromagnetic interference from the bellows while allowing the bellows to perform its vacuum isolation and extension/retraction functions.
2Reliability
If stainless steel bellows are used in radio-frequency environment, then vacuum isolation function is maintained, but thermal energy loss increases due to higher resistivity
Solution Approach 1:
The bellows is constructed from thin stainless steel foil layers instead of thick solid steel. This reduces the resistivity and associated thermal energy loss while maintaining the vacuum isolation function. The thin film structure minimizes the path for RF current flow, reducing I²R losses.
Solution Approach 2:
A conductive shielding layer or grounding screen is introduced as an intermediary to provide a low-resistance path for RF currents, bypassing the high-resistivity stainless steel bellows. This mediator reduces thermal energy loss by preventing RF currents from flowing through the bellows material.
3Adaptability or versatility
If stainless steel bellows are used with extension and retraction capability, then adaptability to variable electrode gap is improved, but impedance stability deteriorates due to changing capacitance and inductance
Solution Approach 1:
The bellows is divided into multiple thin foil layers that can flex independently during extension and retraction. This segmentation allows the structure to accommodate variable electrode gaps while minimizing changes in overall capacitance and inductance, as the distributed structure reduces the impact of positional changes on electrical properties.
Solution Approach 2:
A radio-frequency shielding structure is introduced as an intermediary that provides a stable reference potential and blocks variable electromagnetic fields generated by bellows movement. This shield maintains impedance stability by preventing changes in the bellows position from affecting the radio-frequency circuit characteristics.
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 provides a stable radio-frequency circuit and improved etching rate stability by shielding transverse and longitudinal radio-frequency coupling, reducing thermal energy loss.
Implementation Method 1
a sleeve assembly, including a first sleeve and a second sleeve, wherein the first sleeve is arranged close to the first end of the bellows assembly, and the second sleeve is arranged close to the second end of the bellows assembly; free ends of the first sleeve and the second sleeve are overlapped with each other to form a radio-frequency shielding space when the first sleeve and the second sleeve slide relatively
Data Source
AI summary
Disclosed are a plasma processing device and a retractable sealing part thereof. The retractable sealing part is arranged in or near a radio-frequency circuit of the plasma processing device. The retractable sealing part includes a bellows assembly having a first end and a second end. Isolation rings are added to an upper part and a lower part of the bellows assembly to weaken longitudinal radio-frequency coupling. Metal sleeves are added to an inner side and an outer side of the bellows assembly to shield transverse radio-frequency coupling. The present disclosure effectively shields radio-frequency coupling on the basis of maintaining the functions of vacuum isolation and extension and retraction of the retractable sealing part, thereby obtaining the stable radio-frequency circuit and etching rate.