Plasma Source Power Synchronization to Reduce IMD in Etching
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Solution Overview
Problem
In plasma processing, intermodulation distortion (IMD) occurs due to the application of radio-frequency powers of different frequencies, leading to matching defects and increased reflected wave power, particularly when etching high aspect ratio holes, which affects the etching rate and plasma stability.
Innovation Solution
A control method is introduced where the source power is alternately applied in synchronization with the phase of the bias power's cycle or reference electrical state, allowing for precise control of the HF power's ON/OFF or High/Low states to reduce IMD and optimize the plasma processing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If radio-frequency powers of different frequencies (source power and bias power) are applied simultaneously to generate plasma and draw ions, then the etching process can proceed, but intermodulation distortion occurs causing matching defects and increased reflected wave power
Solution Approach 1:
The patent applies periodic action by synchronizing the source power application with the bias power cycle. The source power is supplied during specific phases (e.g., when bias power is positive or negative) and suppressed during other phases, creating a periodic on/off pattern that prevents intermodulation distortion while maintaining etching productivity
Solution Approach 2:
The patent segments the source power application into distinct time periods corresponding to different phases of the bias power cycle. By dividing the continuous source power into discrete segments applied only during appropriate phases, the system avoids the harmful intermodulation effects that occur when both powers are applied simultaneously
2Quantity of substance
If source power is continuously applied to generate plasma, then plasma density is maintained, but intermodulation distortion increases causing matching defects
Solution Approach 1:
The patent uses periodic action by applying source power only during specific phases of the bias power cycle rather than continuously. This periodic application maintains sufficient plasma density during active phases while eliminating the continuous intermodulation distortion that occurs with simultaneous continuous application of both powers
Solution Approach 2:
The patent extracts or removes the source power during phases when bias power is applied, preventing the harmful interaction. By taking out the source power during specific time periods and only reintroducing it when appropriate, the system eliminates intermodulation distortion while preserving plasma generation capability
3Quantity of substance
If bias power is applied to draw ions, then ion flux to the substrate increases, but reflected wave power increases due to impedance mismatch
Solution Approach 1:
The patent applies periodic action by suppressing source power during the phases when bias power is active. This timing coordination ensures that ion drawing occurs without the interfering source power, reducing reflected wave power while maintaining ion flux to the substrate
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 method effectively reduces IMD, improves plasma generation efficiency, and enhances the etching process by controlling the amount and quality of radicals and ions, particularly in high aspect ratio etching, thereby stabilizing the plasma processing and increasing etching rates.
Implementation Method 1
supplying a bias power to a first electrode that places a workpiece thereon
Implementation Method 2
supplying a source power having a frequency higher than that of the bias power into a plasma processing space
Implementation Method 3
a source power that is a radio-frequency power for generating plasma
Implementation Method 4
alternately applying the first state and the second state of the source power in synchronization with a signal synchronized with a cycle of a radio frequency of the bias power
Data Source
AI summary
A control method of a plasma processing apparatus including a first electrode that places a workpiece thereon includes supplying a bias power to the first electrode, and supplying a source power having a frequency higher than that of the bias power into a plasma processing space. The source power has a first state and a second state. The control method further includes a first control process of alternately applying the first state and the second state of the source power in synchronization with a signal synchronized with a cycle of a radio frequency of the bias power, or a phase within one cycle of a reference electrical state that represents any one of a voltage, current, and electromagnetic field measured in a power feeding system of the bias power.