Plasma Processing System RF Power Modulation
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Solution Overview
Problem
Capacitively coupled plasma processing systems face challenges in efficiently controlling the plasma generation and substrate processing due to limitations in power source configurations, which affect the uniformity and effectiveness of plasma etching and dissociation processes.
Innovation Solution
A plasma processing system with a controller managing RF, bias, and DC power sources to alternate power levels and frequencies, adjusting the direct-current voltage polarity and absolute value across sub-periods to optimize electron supply and gas dissociation, ensuring precise control over substrate potential and plasma conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single RF power source is used for plasma generation, then the system structure is simple, but the control precision and plasma uniformity are insufficient
Solution Approach 1:
The patent divides the single RF power source into multiple independent RF power sources (first RF power source and second RF power source), each capable of independent control. This segmentation enables precise control of different plasma regions while maintaining relatively simple individual source structures, resolving the contradiction between control precision and system complexity.
Solution Approach 2:
The patent implements dynamic control by allowing the first and second RF power sources to operate at different power levels and frequencies that can be adjusted independently over time. This dynamic adjustment capability enables optimization of plasma conditions during different processing stages, achieving high control precision without requiring an overly complex fixed structure.
2Quantity of substance
If continuous high power is applied for plasma generation, then plasma density is high, but substrate damage and non-uniform processing occur
Solution Approach 1:
The patent employs periodic modulation of the first and second RF power sources, alternating between high power and low power states. This periodic action maintains high average plasma density while preventing continuous high-power exposure that causes substrate damage, effectively resolving the contradiction between plasma density and substrate protection.
Solution Approach 2:
The patent applies different power levels to different spatial regions by using separate RF power sources for different electrode regions. This allows high power to be applied only where high plasma density is needed, while other regions receive lower power to avoid substrate damage, achieving local optimization that resolves the contradiction.
3Adaptability or versatility
If multiple power sources with different frequencies are used, then plasma control flexibility is improved, but system complexity and control difficulty increase
Solution Approach 1:
The patent segments the control system into independent control modules for each RF power source, allowing each to operate at its optimized frequency without interfering with others. This modular segmentation provides flexibility in plasma control while keeping individual control circuits relatively simple, resolving the contradiction between flexibility and complexity.
4Productivity
If DC voltage is continuously applied to upper electrode, then plasma generation efficiency is high, but electron supply control precision deteriorates
Solution Approach 1:
The patent applies periodic modulation to the DC voltage on the upper electrode, alternating between high voltage states for efficient plasma generation and low voltage states for precise electron supply control. This temporal segmentation resolves the contradiction by achieving both high efficiency and high precision at different moments within the same processing 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 configuration allows for adjusted electron supply and controlled gas dissociation, enhancing the precision and effectiveness of plasma processing by maintaining stable plasma conditions and optimizing substrate treatment.
Implementation Method 1
The capacitively coupled plasma processing apparatus generates plasma from a gas in the chamber by generating a radio frequency electric field between the upper electrode and the lower electrode
Implementation Method 2
The DC power source is configured to apply a first negative DC voltage to the upper electrode during the first sub-period and apply a second negative DC voltage to the upper electrode during the second sub-period
Data Source
AI summary
In a disclosed plasma processing system, radio frequency power is supplied in a first period to generate plasma, and the power lever of the radio frequency power is set to a reduced power level in a second period. In the second period, bias power is applied to a lower electrode of a substrate support. The bias power changes a potential of the substrate within each cycle that is defined at a second frequency. In the second period, a direct-current voltage is applied to the upper electrode. The direct-current voltage is set such that within each cycle that is defined at the second frequency, a polarity thereof in a first sub-period is negative and an absolute value thereof in the first sub-period is larger than an absolute value thereof in a second sub-period.