Pulsed RF Plasma Etching Timing for High-Aspect-Ratio Profile Control
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Solution Overview
Problem
In plasma processing, especially for high aspect ratio structures, existing technologies face challenges in controlling ion energy, ion incident angle, radical flux, ion flux, and byproduct amounts, leading to shape abnormalities and reduced etching performance.
Innovation Solution
A plasma processing apparatus and method that utilize pulse-shaped radio frequency (RF) power for both the source and bias RF signals, with controlled timing and power levels to manage the plasma conditions, ensuring precise control over ion energy, angle, and radical flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If continuous RF power is supplied to maintain plasma, then plasma stability is improved, but control precision over ion energy and radical flux deteriorates
Solution Approach 1:
The patent applies periodic pulsing of both source RF power and bias RF power to achieve precise control over plasma parameters. By periodically switching the RF power supply on and off with specific duty cycles and timing, the system can dynamically control ion energy, radical flux, and ion flux while maintaining overall plasma stability through the periodic regeneration of plasma during each cycle.
2Productivity
If high ion energy is used to improve etching speed, then productivity is improved, but shape control of high aspect ratio structures deteriorates
Solution Approach 1:
The patent uses periodic pulsing of bias RF power in combination with source RF power to achieve high etching speeds while maintaining shape control. During the plasma on-period, both source and bias RF power are supplied to generate high ion energy for fast etching. During the off-period, plasma is extinguished to allow byproduct removal and prevent excessive ion bombardment that would damage sidewalls, thus maintaining vertical profiles in high aspect ratio structures.
Solution Approach 2:
The patent applies preliminary pulsing of bias RF power before the main etching phase to prepare the plasma conditions. By pre-ionizing the gas and establishing controlled ion flux before full power etching begins, the system achieves better shape control from the outset of the etching process, preventing sidewall damage while maintaining high etching rates.
3Device complexity
If synchronized pulse sequences are used for source and bias RF, then device complexity is reduced, but etching performance uniformity deteriorates
Solution Approach 1:
The patent employs periodic pulsing with deliberately different timing sequences for source RF and bias RF power. The source RF and bias RF are pulsed with different duty cycles and phase relationships, creating distinct temporal patterns that optimize both plasma generation and ion bombardment control. This asymmetric periodic control achieves uniform etching performance across the substrate while maintaining manageable device complexity through standardized pulse generation circuits.
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 enhances the plasma etching performance by minimizing shape abnormalities and improving the uniformity and accuracy of high aspect ratio feature etching, while also reducing byproduct accumulation.
Implementation Method 1
a source RF generator (31a) coupled to the plasma processing chamber (10) and configured to generate electromagnetic energy
Implementation Method 2
a bias RF generator (31b) coupled to the substrate support (11a) and configured to generate electromagnetic energy
Implementation Method 3
The plasma processing apparatus (1) includes a plasma processing chamber (10)
Data Source
AI summary
A plasma processing apparatus includes: a plasma processing chamber; a substrate support disposed in the plasma processing chamber; a source RF generator coupled to the plasma processing chamber, and configured to generate a pulse source RF signal including a plurality of source cycles; and a bias RF generator coupled to the substrate support, and configured to generate a pulse bias RF signal. A transition timing to the bias operating state in each bias cycle is delayed with respect to a transition timing to the source operating state in a corresponding source cycle, the source non-operating period overlaps with the bias non-operating period, and the bias operating period in each bias cycle overlaps with the source operating period in the next source cycle.