Plasma Processing Apparatus Impedance Matching
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Solution Overview
Problem
Conventional plasma processing apparatuses face challenges in maintaining stable matching operations when using high frequency powers with different pulse frequencies, leading to unstable matching device performance due to periodic variations in plasma impedance.
Innovation Solution
A plasma processing apparatus with separate matching devices for each high frequency power supply, utilizing variable reactance elements and impedance sensors to control reactance and calculate average load impedance, allowing for stable matching operations even when pulse frequencies differ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pulse modulation is applied to high frequency power for plasma generation, then charging damage is suppressed and process reliability is improved, but matching device stability deteriorates due to periodic impedance variations
Solution Approach 1:
The patent applies periodic pulse modulation to the high frequency power supplied to the plasma generation electrode. By controlling the duty ratio and frequency of the pulse signal, the system periodically switches between plasma generation and non-generation states, which suppresses charging damage to the gate oxide film while maintaining process reliability. The periodic nature of this modulation is the core mechanism that resolves the technical contradiction.
Solution Approach 2:
The patent changes the operational parameters of the high frequency power supply by introducing pulse modulation with variable duty ratios and frequencies. This parameter change allows the system to control plasma generation dynamically, suppressing charging damage while managing the periodic impedance variations through coordinated control of multiple power supplies.
2Adaptability or versatility
If different pulse frequencies are used for plasma generation and ion attraction, then process control flexibility is improved, but matching device performance deteriorates due to unstable matching operations
Solution Approach 1:
The patent segments the plasma processing system into two independent high frequency power supply channels: one for plasma generation and another for ion attraction. Each channel can operate at different pulse frequencies and duty ratios, providing process control flexibility. The segmentation allows independent optimization of each function while maintaining overall system coordination through separate matching devices.
Solution Approach 2:
The patent employs a universal plasma processing apparatus configuration that can simultaneously support multiple high frequency power supplies operating with different pulse characteristics. This multi-functionality enables the system to achieve both plasma generation and ion attraction with optimized parameters, while the matching devices are designed to handle varying impedance conditions universally.
3Manufacturing precision
If high frequency power with frequency equal to or higher than 40 MHz is used, then etching uniformity and selectivity are improved, but charging damage increases due to reduced ion energy at lower pressure
Solution Approach 1:
The patent applies periodic pulse modulation to the high frequency power (40 MHz or higher) supplied to the plasma generation electrode. This periodic switching between plasma generation and non-generation states limits the continuous accumulation of electric charges on the gate oxide film, thereby suppressing charging damage while maintaining the benefits of high frequency operation for etching uniformity and selectivity.
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
Enables stable and accurate matching operations for high frequency powers with different frequencies, reducing the impact of plasma impedance variations and maintaining process reliability.
Implementation Method 1
Electrons are accelerated in a high frequency electric field generated between the two facing electrodes by applying the high frequency power, and plasma is generated as a result of ionization by collision between the electrons and a processing gas.
Implementation Method 2
a first matching device, having a first variable reactance element and a first impedance sensor provided on the first high frequency transmission line, configured to control a reactance of the first variable reactance element such that a first load impedance measurement value outputted from the first impedance sensor is equal to or approximate to a first matching point corresponding to an output impedance of the first high frequency power supply
Data Source
AI summary
In a plasma processing apparatus, when pulse-modulating the high frequency power RF1 for plasma generation and the high frequency power RF2 for ion attraction with a first pulse PS1 and a second pulse PS2 having different frequencies, respectively, an impedance sensor 96A in a matching device 40 of a plasma generation system calculates an average value (primary moving average value ma) of an load impedance on a high frequency transmission line 43 for each cycle of the second pulse PS2 having a lower frequency, and outputs a load impedance measurement value based on those average values of the load impedance. Then, a matching controller 94A controls reactances of reactance elements XH1 and XH2 within a matching circuit 88A such that the load impedance measurement value is equal or approximate to a matching point (50Ω).