Plasma Reactor RF Tuning With External Variable Capacitance
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Solution Overview
Problem
Existing plasma processing technologies face challenges in uniformly distributing low frequency RF power to the substrate edge area, leading to inconsistent etching speed and direction, which affects the yield and uniformity of semiconductor chip processing, due to limitations in tuning mechanisms that often result in complex structures, high costs, and difficulty in precise control.
Innovation Solution
A plasma reactor with a variable impedance device comprising capacitors and switches connected in series, allowing for precise tuning of low frequency RF power distribution by adjusting capacitance values, which is mounted outside the reaction chamber to minimize complexity and cost, and includes an annular electrode and conductive connections to bypass impedance issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric fluid supply pipeline and hermetic cavity are provided inside the reaction chamber to tune bias RF power distribution, then the processing result drift can be compensated, but the structure complexity and cost increase significantly
Solution Approach 1:
The patent extracts the variable impedance device from the reaction chamber interior and places it in the mounting space below the hermetic baffle plate. This removes the complex fluid supply pipeline and hermetic cavity requirements from the reaction chamber, significantly reducing structure complexity while maintaining the ability to compensate processing result drift through electrical impedance adjustment.
Solution Approach 2:
The patent replaces the mechanical/fluid-based tuning system (dielectric fluid supply pipeline) with an electrical system (variable impedance device with capacitors and switches). This substitution eliminates the need for hermetic cavities and fluid management infrastructure, reducing both structure complexity and maintenance requirements while achieving the same goal of compensating processing drift.
2Manufacturing precision
If a mechanical driving device is provided in the reaction chamber to move the coupling ring or focus ring, then the electric field distribution can be adjusted, but particle contamination occurs to movable parts
Solution Approach 1:
The patent replaces the mechanical driving device that physically moves the coupling ring or focus ring with an electrical impedance adjustment system. The variable impedance device modifies the electrical characteristics of the existing components without requiring physical movement, thereby eliminating particle contamination of movable parts while maintaining precise electric field distribution control.
Solution Approach 2:
The patent introduces a variable impedance device as an intermediary element that indirectly controls the electric field distribution through electrical parameter adjustment rather than direct mechanical manipulation. This intermediary approach allows precise control of the coupling ring and focus ring electrical characteristics without physical contact or movement, preventing particle contamination.
3Productivity
If the focus ring is retained in plasma for long term, then continuous processing is achieved, but the focus ring surface material is corroded and height decreases
Solution Approach 1:
The patent implements a feedback mechanism where the variable impedance device continuously monitors and compensates for the focus ring degradation. By adjusting the impedance parameters in response to measured processing drift, the system compensates for focus ring height decrease and material corrosion, maintaining consistent processing results over extended operation periods without requiring frequent focus ring replacement.
Solution Approach 2:
The patent applies beforehand cushioning by pre-configuring the variable impedance device to compensate for anticipated focus ring degradation. The system proactively adjusts impedance parameters to counteract the expected height decrease and material corrosion that will occur during long-term plasma exposure, maintaining processing stability before significant degradation occurs.
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 solution enables fine and precise tuning of low frequency RF power distribution, improving the uniformity of substrate processing by maintaining consistent sheath height and plasma density across the substrate, reducing the need for frequent focus ring replacements and avoiding particle contamination.
Implementation Method 1
a variable impedance device comprising capacitors and switches connected in series, allowing for precise tuning of low frequency RF power distribution by adjusting capacitance values
Implementation Method 2
many plasma processors are needed during the manufacturing procedure of semiconductor chips, which processors perform processing such as plasma etching and CVD (Chemical Vapor Deposition) to substrates
Implementation Method 3
a bias RF power is used for controlling the thickness of a sheath formed on the upper surface of the substrate and the focus ring, wherein the thicknesses of the sheath determines energy and direction of the ions in the plasma incident to the substrate
Data Source
AI summary
The present disclosure provides a plasma reactor having a function of tuning low frequency RF power distribution, comprising: a reaction chamber in which an electrically conductive base is provided, the electrically conductive base being connected to a low frequency RF source via a first match, an electrostatic chuck being provided on the electrically conductive base, an upper surface of the electrostatic chuck being configured for fixing a to-be-processed substrate, an outer sidewall of the electrically conductive base being coated with at least one layer of plasma corrosion-resistance dielectric layer, a coupling ring made of a dielectric material surrounding an outer perimeter of the base, a focus ring being disposed above the coupling ring, the focus ring being arranged surround the electrostatic chuck and be exposed to a plasma during a plasma processing procedure; the plasma reactor further comprising an annular electrode that is disposed above the coupling ring but below the focus ring; a wire, a first end of which is electrically connected to the base, and a second end of which is connected to the annular electrode, a variable capacitance being serially connected to the wire.