Plasma Source Power Synchronization to Reduce Etching IMD
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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 with high aspect ratio holes, where the etching rate decreases and IMD increases, affecting the control of radicals and ions.
Innovation Solution
A control method is introduced where the source power with a higher frequency is alternately applied in synchronization with the phase of the bias power's cycle or reference electrical state, reducing IMD by controlling the impedance matching and ion energy, thereby improving plasma density and etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radio-frequency powers of different frequencies are applied to generate plasma and draw ions, then plasma generation and ion control are achieved, but intermodulation distortion occurs causing matching defects and increased reflected wave power
Solution Approach 1:
The patent applies periodic action by alternately switching the source power between ON and OFF states in synchronization with the bias power cycle. This periodic modulation reduces intermodulation distortion by ensuring the source power is only present when the bias power is in a state that minimizes IMD generation, thereby maintaining plasma generation stability while reducing harmful interference
Solution Approach 2:
The patent implements preliminary anti-action by preemptively controlling the source power timing to prevent intermodulation distortion from occurring. By synchronizing the source power application with the bias power phase and alternately switching it based on the RF cycle, the system proactively avoids the conditions that would generate IMD, rather than attempting to correct it after occurrence
2Quantity of substance
If source power is continuously applied to maintain plasma density, then plasma generation efficiency is maintained, but intermodulation distortion increases affecting etching control
Solution Approach 1:
The patent uses periodic action by alternately switching source power between ON and OFF states in synchronization with the bias power RF cycle. This maintains adequate plasma density through periodic replenishment while significantly reducing intermodulation distortion, thereby improving etching rate control and preventing the distortion-related issues that would otherwise hinder operational ease
3Speed
If bias power is applied to draw ions for high aspect ratio etching, then ion energy is increased for deep etching, but intermodulation distortion increases reducing etching uniformity
Solution Approach 1:
The patent applies periodic action by synchronizing source power alternation with the bias power RF cycle. This maintains high ion energy during the bias power's ion-accelerating phases while reducing intermodulation distortion through coordinated power management, thereby preserving both the ion energy needed for deep etching and the etching uniformity that would otherwise be degraded by IMD
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, enhances plasma generation efficiency, and maintains high ion energy for deep etching, improving the etching rate and shape while stabilizing the plasma processing apparatus.
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
supplying a bias power to the first electrode... 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.