Edge Impedance Circuit for Plasma Etching Uniformity
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Solution Overview
Problem
In semiconductor substrate treating processes, the ion flux direction in the edge region changes due to etching, leading to non-uniform etching and reduced yield, while harmonics generated in the plasma cause an imbalance in etching between the center and edge regions.
Innovation Solution
A substrate treating apparatus and method that includes an edge impedance control circuit with a harmonics control circuit unit and an ion flux control circuit unit, using variable capacitors and band stop filters to control harmonics and ion flux direction, thereby improving etching uniformity and extending the use time of the edge ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If RF plasma is coupled to the edge ring using a coupling ring and ion flux direction is controlled using a variable element in a RF filter, then the ion flux direction of the edge region is controlled, but non-linearity of plasma sheath causes imbalance in etching amount between center and edge regions
Solution Approach 1:
The patent divides the control function into two separate circuits: a harmonics control circuit unit with a first variable capacitor specifically for controlling plasma harmonics, and an ion flux control circuit unit with a second variable element for controlling ion flux direction. This segmentation allows independent optimization of each control function, preventing the trade-off between ion flux control and etching uniformity that plagued the conventional single-circuit approach.
Solution Approach 2:
The patent introduces a band stop filter as an intermediary component in the ion flux control circuit unit to eliminate harmful harmonics before they affect the plasma sheath. This intermediary element mediates between the RF power source and the plasma, blocking third harmonic signals that cause non-linear plasma sheath effects and etching uniformity problems.
2Quantity of substance
If harmonics are not controlled in the plasma, then the plasma density in the central region increases, but this causes imbalance in etching amount between center and edge regions
Solution Approach 1:
The patent extracts and separately controls the harmonics component from the plasma system using a dedicated harmonics control circuit unit. By extracting the third harmonic control function into a separate circuit with a first variable capacitor, the system can independently manage harmonics without affecting the main plasma density control, thereby preventing etching uniformity imbalance.
Solution Approach 2:
The band stop filter acts as an intermediary that selectively removes harmful harmonic frequencies from the RF signal before it reaches the plasma. This allows the main plasma density to be maintained while specifically eliminating the third harmonic component that causes non-linear plasma sheath effects and etching uniformity problems.
3Productivity
If the edge ring is used for extended periods, then productivity increases, but the ion flux direction changes due to edge ring etching, reducing yield
Solution Approach 1:
The patent implements feedback control mechanisms in both the harmonics control circuit unit and the ion flux control circuit unit, allowing real-time adjustment of the first and second variable elements based on plasma conditions. This feedback system continuously monitors and corrects ion flux direction changes caused by edge ring etching, maintaining process uniformity over extended production periods.
Solution Approach 2:
The patent uses variable elements (first variable capacitor and second variable element) that can dynamically adjust their parameters in response to changing plasma conditions. This dynamic adjustment capability allows the system to compensate for edge ring etching effects over time, maintaining reliable ion flux direction control throughout extended production cycles.
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 effectively improves etching uniformity and increases the use time of the edge ring by simultaneously controlling harmonics and ion flux direction, addressing the imbalances caused by plasma harmonics in conventional processes.
Implementation Method 1
an RF power source for supplying an RF signal to excite the process gas to a plasma state
Implementation Method 2
the harmonics control circuit unit may include a first variable capacitor
Implementation Method 3
the ion flux control circuit unit may include a second variable capacitor
Data Source
AI summary
A substrate treating apparatus is disclosed. The apparatus includes a process chamber having a treating space defined therein, a support unit for supporting a substrate in the treating space, a gas supply unit for supplying process gas into the treating space, and an RF power source for supplying an RF signal to excite the process gas to a plasma state, wherein the support unit includes an edge ring surrounding the substrate, a coupling ring disposed below the edge ring and including an electrode therein, and an edge impedance control circuit connected to the electrode wherein the edge impedance control circuit includes a harmonics control circuit unit for controlling harmonics caused by the RF power source, and an ion flux control circuit unit for controlling an ion flux in an edge region of the substrate.