Multi-frequency Power Modulation for High Aspect Ratio Etching
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Solution Overview
Problem
The increasing complexity and aspect ratios in semiconductor integrated circuits require advanced etching processes that achieve selective material removal and precise profile control, which existing plasma etching techniques struggle to meet effectively.
Innovation Solution
A modulated plasma etching process is employed, involving a power modulation cycle with distinct first and second power sequences, where the power levels and frequencies are varied to selectively etch one material over another, reducing surface charging and feature clogging while enhancing etch product exhaustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used, then the etching process can be performed, but selectivity and profile control deteriorate with increasing aspect ratios
Solution Approach 1:
The patent applies periodic modulation of plasma power at multiple frequencies during the etching process. The power is modulated between different levels in a cyclic manner, creating periodic variations in plasma density and ion flux. This periodic action allows for controlled etching that maintains profile precision even in high aspect ratio features by alternating between high etch rate phases and low etch rate phases for surface relaxation
Solution Approach 2:
The patent dynamically adjusts plasma process parameters during etching by implementing time-varying power modulation. The system transitions from static power delivery to dynamic power control, where power levels are continuously adjusted according to a modulation cycle. This dynamic control enables adaptation to changing etch conditions, maintaining selectivity and profile control throughout the etching of deep features
2Manufacturing precision
If conventional plasma etching is used, then the etching process can be performed, but selectivity between materials deteriorates
Solution Approach 1:
The patent uses periodic power modulation to create alternating high and low plasma density phases. During high power phases, etching proceeds rapidly with high ion flux. During low power phases, the reduced ion flux allows for surface relaxation and volatile byproduct evacuation. This periodic cycling maintains material selectivity by preventing excessive heating and polymer buildup that would occur in continuous high-power etching of deep features
Solution Approach 2:
The patent changes plasma process parameters dynamically by modulating power at multiple frequencies. The power level transitions between different states according to the modulation scheme, creating time-varying plasma conditions. This parameter modulation optimizes etch selectivity by adjusting the balance between physical sputtering and chemical reactions differentially for various materials throughout the etching process
3Productivity
If continuous high power is applied, then etching speed increases, but surface charging and feature clogging increase
Solution Approach 1:
The patent implements periodic power modulation that alternates between high power (for etching) and low power (for surface relaxation) phases. This periodic cycling reduces cumulative surface charging by allowing charge dissipation during low power intervals. The modulation frequency is selected to match the time scale of charge accumulation and relaxation, preventing excessive charge buildup that would repel ions and reduce etching efficiency in deep features
Solution Approach 2:
The patent maintains continuous etching progress through multi-frequency power modulation that ensures useful action occurs throughout the cycle. Rather than stopping etching entirely, the system continues with reduced power during relaxation phases, maintaining a continuous but modulated etching process. This approach preserves productivity while periodically reducing harmful effects through power variation
4Productivity
If continuous high power is applied, then etching speed increases, but feature clogging increases
Solution Approach 1:
The patent applies periodic power modulation with cycles that alternate between high power etching phases and low power evacuation phases. During low power phases, the reduced ion flux and continued radical transport allow volatile etch byproducts to evacuate from deep features more effectively. This periodic evacuation prevents polymer buildup and feature clogging while maintaining overall etching speed through the high power phases
Solution Approach 2:
The patent uses brief high power pulses that rapidly advance the etch front through difficult-to-reach regions before byproducts can accumulate. The modulation scheme includes short high power intervals that 'rush through' potential clogging zones, followed by longer low power intervals that allow complete evacuation. This skipping approach prevents clogging by not allowing continuous conditions that would permit byproduct accumulation
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 enables improved selectivity and profile control during etching, ensuring efficient removal of specific materials and reducing feature clogging, thereby supporting the miniaturization and complexity demands of semiconductor manufacturing.
Implementation Method 1
performing a modulated plasma etching process to selectively remove the first material at a rate greater than removing the second material
Data Source
AI summary
A method of etching a substrate is described. The method includes disposing a substrate having a surface exposing a first material and a second material in a processing space of a plasma processing system, and performing a modulated plasma etching process to selectively remove the first material at a rate greater than removing the second material. The modulated plasma etching process includes a power modulation cycle composed of applying a first power modulation sequence to the plasma processing system, and applying a second power modulation sequence to the plasma processing system, the second power modulation sequence being different than the first power modulation sequence.