RF Antenna Buffer Area Suppresses Discharge in Plasma Chamber
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Solution Overview
Problem
In inner-antenna plasma processing apparatuses, electric discharges between the radio-frequency antenna and the protective tube lead to energy wastage and hinder plasma generation in the vacuum chamber, as the induction electric field is consumed by discharges in the space between them.
Innovation Solution
A radio-frequency antenna unit with a buffer area between the antenna and the protective tube, where electron acceleration is suppressed, either by vacuum, insulator, or gas, such as glass wool, to prevent continuous electric discharges, and a gas seal to control pressure independently, along with a highly resistive coating on the protective tube to enhance plasma resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective tube is provided around the radio-frequency antenna to prevent sputtering, then the antenna is protected from material loss, but electric discharges occur in the space between the antenna and protective tube causing energy loss and hindering plasma generation
Solution Approach 1:
A buffer area is introduced as an intermediary space between the radio-frequency antenna and the protective tube. This buffer area, maintained at a higher pressure than the vacuum chamber, acts as a mediator that prevents direct electric discharge between the antenna and protective tube by providing a region where electrons are rapidly scattered, thereby eliminating the harmful energy loss while preserving the protective function.
Solution Approach 2:
The pressure parameter is changed in the space between the antenna and protective tube by introducing a buffer area at higher pressure compared to the vacuum chamber. This pressure change fundamentally alters the electrical discharge characteristics, preventing continuous discharge and converting the space from a harmful region into a protective buffer zone.
2Length of stationary object
If the space between the radio-frequency antenna and protective tube is evacuated to the same pressure as the vacuum chamber, then the protective tube can be positioned close to the antenna, but electric discharges occur consuming the induction electric field and preventing plasma generation
Solution Approach 1:
The buffer area serves as an intermediary region that allows the protective tube to be positioned close to the antenna while preventing harmful electric discharges. By maintaining different pressure conditions in this intermediary zone compared to the vacuum chamber, the system enables close spacing without sacrificing plasma generation efficiency.
3Loss of energy
If a buffer area is introduced between the radio-frequency antenna and protective tube to suppress electric discharge, then energy loss is reduced and plasma generation is improved, but the device structure becomes more complex
Solution Approach 1:
The buffer area is implemented using a flexible membrane or thin film structure that separates the buffer region from the vacuum chamber. This approach achieves the desired pressure differentiation and discharge suppression while maintaining a relatively simple and compact device structure, avoiding excessive complexity.
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 configuration effectively suppresses electric discharges between the antenna and the protective tube, allowing for efficient generation of high-density plasma in the vacuum chamber by conserving electromagnetic wave energy and preventing material contamination.
Implementation Method 1
a radio-frequency electric current is applied to the radio-frequency antenna to form an induction electric field around the radio-frequency antenna, and thereby a discharge plasma is induced in the vacuum chamber
Implementation Method 2
the acceleration of electrons is suppressed. The buffer area can be formed, for example, with a vacuum or an insulator... the existence of glass fibers can suppress the acceleration of electrons by a radio-frequency electric field and the ionization of the process gas which occurs due to the acceleration
Implementation Method 3
a gas seal is provided between the buffer area and the vacuum chamber. By using such a gas seal, the pressure of the gas in the buffer area can be controlled independently of the pressure in the vacuum chamber
Data Source
AI summary
The present invention aims at providing a radio-frequency antenna unit capable of generating a high-density discharge plasma in a vacuum chamber. The radio-frequency antenna unit according to the present invention includes: a radio-frequency antenna through which a radio-frequency electric current can flow; a protective tube made of an insulator provided around the portion of the radio-frequency antenna that is in the vacuum chamber; and a buffer area provided between the radio-frequency antenna and the protective tube. The “buffer area” refers to an area where an acceleration of electrons is suppressed, and it can be formed, for example, with a vacuum or an insulator. Such a configuration can suppress an occurrence of an electric discharge between the antenna and the protective tube, enabling the generation of a high-density discharge plasma in the vacuum chamber.