Pulsed Plasma Control for Etching Uniformity in Narrow-Gap Chambers
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Solution Overview
Problem
Plasma processing chambers experience non-uniformity issues, particularly in narrow-gap chambers and larger substrates, due to varying by-product gas concentrations across the substrate, leading to aspect ratio dependent etching (ARDE) problems.
Innovation Solution
The effective gas residence time in plasma processing chambers is reduced by modulating RF power to enter a reduced mode, where plasma generation energy is lowered or stopped for a portion of the processing time, allowing by-product gases to travel without engaging in secondary reactions, and then returning to full power, monitored using light emission and absorption techniques to maintain uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous plasma generation is maintained to ensure sufficient etching rate, then productivity is improved, but gas residence time increases causing non-uniformity and ARDE problems
Solution Approach 1:
The patent applies periodic pulsed plasma generation where the plasma is turned on and off in cycles. During the on-phase, etching occurs at high rate; during the off-phase, by-product gases are pumped away without new by-products being generated. This periodic action reduces effective gas residence time and improves etching uniformity across the substrate while maintaining overall productivity through optimized pulse duty cycles.
2Manufacturing precision
If RF power is continuously supplied to maintain plasma for sufficient processing, then manufacturing precision is maintained, but energy consumption increases and by-product accumulation worsens
Solution Approach 1:
The patent implements periodic RF power supply to generate pulsed plasma rather than continuous plasma. The RF power is supplied in pulses with specific duty cycles, where plasma is generated only during the on-phase. This reduces total energy consumption while maintaining process uniformity through controlled plasma exposure times, preventing by-product accumulation that occurs with continuous plasma generation.
Solution Approach 2:
The patent uses preliminary action by introducing reactant gas and preparing the chamber environment before plasma generation begins. During the plasma off-phase, the system prepares for the next pulse by ensuring proper gas flow and pressure conditions, which allows efficient plasma ignition and reduces the energy required to maintain plasma stability during the on-phase.
3Manufacturing precision
If plasma generation energy is reduced to allow by-product gas removal, then gas residence time is reduced improving uniformity, but etching rate decreases
Solution Approach 1:
The patent resolves this contradiction by using periodic plasma generation with optimized pulse width and duty cycle. During the plasma on-phase, high etching rate is achieved with full plasma generation energy. During the plasma off-phase, etching stops but by-product removal continues through gas pumping. The cumulative effect over multiple cycles achieves both high etching rate and improved uniformity, as the effective gas residence time is reduced while maintaining sufficient total etching exposure.
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 approach improves etching uniformity by reducing the effective gas residence time, addressing ARDE and non-uniformity issues by controlling by-product gas concentrations and polymer precursor deposition, enhancing etch directionality and selectivity.
Implementation Method 1
plasma generation may employ capacitively coupled plasma technology, inductively coupled plasma technology, electron-cyclotron technology, microwave technology, etc.
Implementation Method 2
reactant gas (which may employ one or multiple types of gases) is released into the plasma processing region and energized to form a plasma
Implementation Method 3
monitored using light emission and absorption techniques to maintain uniformity
Implementation Method 4
monitored using light emission and absorption techniques
Data Source
AI summary
Methods and apparatuses for controlling plasma generation in a plasma processing chamber to reduce an effective residence time of by-product gases or to control in real time the concentration of certain polymer pre-cursors or reaction by-products in the plasma processing chamber are disclosed. The gas residence time is “effectively” reduced by reducing the plasma reaction for at least a portion of the process time. Thresholds can be provided to control when the plasma reaction is permitted to proceed at the full rate and when the plasma reaction is permitted to proceed at the reduced rate. By reducing the rate of plasma by-product generation at least for a portion of the process time, the by-product gas residence time may be effectively reduced to improve process results.