Plasma Processing RF Phase Control to Reduce IMD
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing plasma processing technologies face challenges in controlling intermodulation distortion (IMD) and maintaining optimal impedance matching when using radio-frequency powers of different frequencies, leading to increased reflected wave power and reduced etching efficiency, particularly in high aspect ratio etching processes.
Innovation Solution
A control method is implemented where the source power is alternately applied in synchronization with the phase of the bias power's cycle, reducing IMD by controlling the application of HF power based on the phase of LF power, thereby optimizing the impedance matching and ion/radical generation.
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 etching process can be performed, but intermodulation distortion occurs and reflected wave power increases
Solution Approach 1:
The source power is applied in a periodic manner synchronized with the bias power cycle. The source power is turned on during the negative half-cycle of the bias power and turned off during the positive half-cycle, creating a periodic action pattern that prevents intermodulation distortion while maintaining etching efficiency
Solution Approach 2:
The timing of source power application is predetermined and synchronized with the bias power phase. By preparing and controlling the source power to be applied at specific phases of the bias power cycle beforehand, the system prevents IMD from occurring in the first place
2Quantity of substance
If source power is continuously applied to maintain plasma density, then plasma generation is sustained, but impedance matching deteriorates and reflected wave power increases
Solution Approach 1:
The source power is applied periodically in synchronization with the bias power cycle rather than continuously. This periodic application maintains plasma density during the active phase while allowing impedance to stabilize during the off-phase, preventing reflected wave power increase
Solution Approach 2:
The source power application is made dynamic by synchronizing it with the varying impedance conditions of the bias power cycle. The system adapts the source power timing to match the dynamic impedance changes, maintaining optimal performance throughout the cycle
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, maintains plasma density, and enhances etching efficiency, especially in high aspect ratio processes, by synchronizing the application of HF and LF powers to align with the phase of the bias power's cycle.
Implementation Method 1
supplying a source power having a frequency higher than that of the bias power into a plasma processing space
Implementation Method 2
source power that is a radio-frequency power for generating plasma
Implementation Method 3
bias power that is a radio-frequency power for drawing ions
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.