Edge Impedance Control Circuit for Plasma Etching Uniformity
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Solution Overview
Problem
Conventional etching processes in semiconductor device fabrication face issues with ion flux directionality changes at the edge region, leading to non-uniform etching and increased plasma density, causing irregular etch amounts between central and edge regions, and are not effectively controlled by existing methods that neglect harmonic components.
Innovation Solution
An apparatus and method that utilize an edge impedance control circuit with harmonic, ion flux, and cable impedance control units, including variable capacitors and band stop filters, to regulate ion directionality and harmonic components, thereby controlling the etching process and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If edge ring etching is used to control ion flux directionality in the edge region, then ion directionality is improved, but harmonic components are generated that increase plasma density in the central region causing irregular etch amounts
Solution Approach 1:
The patent applies band stop filters to remove harmful harmonic components (especially third harmonic) from the RF signal, converting the harmful effect of harmonic generation into a controlled situation where only the fundamental frequency remains, thereby eliminating plasma density irregularities while maintaining ion directionality control
Solution Approach 2:
The patent introduces an impedance control circuit as an intermediary between the RF power source and the edge ring, which includes variable capacitors and band stop filters to mediate the RF signal and prevent harmonic components from reaching the plasma generation region
2Device complexity
If conventional design process is used, then device complexity is reduced, but harmonic signals especially third harmonic signal are not controlled causing plasma density increase
Solution Approach 1:
The patent extracts and removes the harmful third harmonic component from the RF signal using a band stop filter tuned to the third harmonic frequency, separating the harmful frequency component from the fundamental frequency to prevent plasma density irregularities without significantly increasing circuit 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 approach improves etching uniformity, extends the usage time of the etch ring, and adjusts etch rates by controlling ion flux and harmonic components, addressing the irregularities caused by RF cable length differences and harmonic signals.
Implementation Method 1
The plasma is generated due to a significantly high temperature, a strong electric field, or radio frequency electromagnetic fields
Implementation Method 2
the direction of the ion flux may be changed in the edge region due to the etching using an edge ring
Implementation Method 3
a harmonic component generated due to the plasma increases the plasma density in the central region
Data Source
AI summary
An apparatus for treating a substrate is disclosed. The apparatus includes a radio frequency (RF) power source to apply an RF signal to excite a process gas to be in a plasma state. A supporting unit to support the substrate includes an edge ring to surround the substrate, a coupling ring disposed under the edge ring and including an electrode in the coupling ring, and an edge impedance control circuit connected with the electrode. The edge impedance control circuit includes a harmonic control circuit unit to control a harmonic generated from the RF power source, an ion flux control circuit unit to adjust an ion flux of an edge region of the substrate, and a cable impedance control circuit unit to adjust an impedance made due to a length of the RF cable.