Pulse-Synchronized Plasma End Point Detection for Cycle Etching
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Solution Overview
Problem
Conventional methods for detecting the end point of plasma processing, such as etching and cleaning, are inaccurate, especially in cycle etching where radio-frequency power is applied in a pulse form, leading to excessive processing and variations in pattern shape.
Innovation Solution
A plasma processing apparatus equipped with a measuring unit to detect changes in voltage, current, and phase difference between voltage and current, synchronized with the pulse cycle of radio-frequency power, allowing for precise detection of the end point of processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional end point detection methods are used in cycle etching, then the detection process is simple, but the detection precision is low leading to excessive processing and pattern variations
Solution Approach 1:
The patent segments the detection process by measuring voltage and current at multiple discrete time points within each pulse cycle (peak voltage time, peak current time, and multiple intermediate times). This segmentation of measurement timing enables precise detection of impedance changes throughout the etching process, resolving the contradiction between simple detection and high precision by distributing measurements across multiple time segments rather than using a single complex measurement system
Solution Approach 2:
The patent implements periodic measurement action by synchronizing voltage and current measurements with the pulse cycle of the radio-frequency power supply. Measurements are taken at regular intervals corresponding to the pulse waveform characteristics, enabling accurate detection of end point conditions while maintaining a systematic and repeatable detection rhythm that balances simplicity with precision
2Productivity
If pulse form radio-frequency power is applied for cycle etching, then productivity is improved, but measurement accuracy for end point detection deteriorates due to periodic power interruption
Solution Approach 1:
The patent applies preliminary action by pre-establishing the relationship between voltage-current phase differences and etching states before the actual etching process. The system stores reference data from standard etching processes, allowing it to compare real-time measurements against known patterns and accurately identify end points even during pulse interruptions, thus maintaining measurement precision while benefiting from high-speed pulse etching
Solution Approach 2:
The patent implements feedback by continuously monitoring voltage and current measurements during pulse etching and comparing them against reference data. The system provides real-time feedback on etching progress and automatically adjusts measurements to account for pulse timing variations, ensuring accurate end point detection despite the periodic power interruption inherent in pulse-form radio-frequency processing
3Measurement precision
If voltage and current measurements are taken at multiple time points synchronized with pulse cycle, then end point detection accuracy is improved, but measurement complexity increases
Solution Approach 1:
The patent applies universality by designing a measurement system that serves multiple functions: it measures voltage, current, phase differences, and impedance changes using the same synchronized measurement framework. This multi-functional approach eliminates the need for separate specialized measurement systems for each parameter, reducing overall system complexity while maintaining high detection accuracy through unified multi-parameter monitoring
Solution Approach 2:
The patent merges voltage and current measurements into a single integrated measurement process that occurs simultaneously at the same time points within each pulse cycle. By combining these measurements and calculating phase differences from the same data set, the system reduces the number of separate measurement systems needed while achieving comprehensive monitoring of etching conditions with high precision
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
Accurately detects the end point of plasma processing, preventing excessive etching and ensuring consistent pattern shapes by synchronizing measurements with the pulse cycle of radio-frequency power.
Implementation Method 1
a radio-frequency power supply configured to supply, to the chamber, radio-frequency power in a pulse form making the gas supplied into the chamber plasma
Data Source
AI summary
A measuring unit is provided in an electrode disposed inside a chamber or a wire connected to the electrode and measures either a voltage or a current. A gas supply unit supplies a gas to be made into plasma into the chamber. A radio-frequency power supply supplies radio-frequency power in a pulse form making the gas supplied into the chamber plasma to the chamber. A detector detects an end point of plasma processing from a change in any of a voltage, a current, and a phase difference between the voltage and the current measured by the measuring unit with a timing synchronized with a cycle of pulses of the radio-frequency power.