Plasma Source Power Synchronization to Suppress IMD in Etching
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Solution Overview
Problem
Existing plasma processing technologies face challenges in controlling the amount and quality of radicals and ions due to intermodulation distortion (IMD), which leads to matching defects and increased reflected wave power.
Innovation Solution
A control method for a plasma processing apparatus that involves supplying a bias power to a first electrode and a source power with a frequency higher than the bias power into a plasma processing space. The source power has two states, and the method includes alternately applying these states in synchronization with a signal synchronized with the cycle of the radio frequency of the bias power or a phase within one cycle of a reference electrical state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If radio-frequency powers of two different frequencies (source power and bias power) are applied simultaneously to generate plasma and draw ions, then the etching process can be performed, but intermodulation distortion (IMD) occurs causing matching defects and increased reflected wave power
Solution Approach 1:
The patent applies periodic action by alternately switching the source power and bias power in a time-division manner rather than applying them simultaneously. The source power is applied during a first time period to generate plasma, and the bias power is applied during a second time period to draw ions, with both operating at the same frequency. This periodic switching eliminates intermodulation distortion while maintaining the etching process capability.
2Reliability
If source power and bias power are applied simultaneously, then plasma generation and ion drawing can occur, but matching defects increase and reflected wave power increases
Solution Approach 1:
The patent implements periodic action by dividing the power application into alternating time periods: source power is applied during the first time period for plasma generation, and bias power is applied during the second time period for ion drawing. Both operate at the same frequency but are time-division multiplexed, which eliminates the simultaneous application that causes matching defects and reduces reflected wave power.
Solution Approach 2:
The patent applies preliminary action by first applying the source power to generate plasma before applying the bias power to draw ions. This sequential preparation ensures that ions are available for drawing when the bias power is applied, maintaining etching effectiveness while avoiding the energy loss associated with simultaneous application.
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 the occurrence of IMD, improves plasma generation efficiency, and allows for precise control of ion energy, thereby enhancing the quality and amount of radicals and ions produced.
Implementation Method 1
supplying a bias power to the first electrode... a bias power that is a radio-frequency power for drawing ions
Implementation Method 2
supplying a source power having a frequency higher than that of the bias power into a plasma processing space... a source power that is a radio-frequency power for generating plasma
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.