Multi-State RF Pulsing for Mask CD Control in Plasma Etching
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Solution Overview
Problem
In plasma etching processes, maintaining an adequate process margin while achieving selective etching of stack layers compared to mask layers is challenging, particularly in high aspect ratio contact etches, where mask selectivity is limited by polymerizing species, leading to mask clogging and reduced critical dimension control.
Innovation Solution
Implementing multi-state pulsing with a no bias and low flux regime to control the mask etch rate, which allows for improved mask selectivity and reduced clogging by trimming and straightening the neck area, thereby widening the process margin and maintaining benefits of both selectivity and etch rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If two-level RF pulsing with low level/off state is used to increase mask selectivity, then mask selectivity is improved, but mask clogging increases due to more passivation at the top of the mask
Solution Approach 1:
The patent applies multi-state pulsing where RF power is periodically modulated through multiple distinct states (high power state for etching, low power/off state for passivation, and intermediate states for polymer management). This periodic switching between different power levels allows the system to alternately enhance mask selectivity through passivation while preventing mask clogging by periodically removing excess polymers, thus resolving the contradiction between improved selectivity and reduced clogging
Solution Approach 2:
The patent changes the RF power parameter dynamically by introducing multiple discrete power states rather than maintaining a single low level/off state. By implementing a multi-state pulsing regime with varying power levels (including intermediate states between high and low), the system optimizes both mask selectivity and polymer deposition control, breaking the tradeoff where increased passivation leads to clogging
2Object-generated harmful factors
If chemistry with less polymer source is used to widen process margin and reduce mask clogging, then mask clogging is reduced, but mask selectivity worsens
Solution Approach 1:
Instead of relying solely on chemistry with less polymer source, the patent uses periodic multi-state pulsing to dynamically control polymer deposition and removal. The low power/off states provide necessary passivation for mask selectivity while the periodic nature of pulsing prevents excessive polymer accumulation, achieving both reduced clogging and maintained selectivity without compromising chemistry performance
Solution Approach 2:
The patent changes the temporal parameters of RF power delivery through multi-state pulsing, introducing duty cycles and timing variations that allow sufficient passivation during low power states while limiting total polymer deposition. This parameter control enables the system to achieve adequate mask selectivity and process margin without requiring chemistry that inherently produces less polymer
3Manufacturing precision
If adequate process margin is maintained while selectively etching stack layer, then selectivity is improved, but process margin is reduced due to limited mask selectivity from polymerizing species
Solution Approach 1:
The patent employs multi-state pulsing with periodic transitions between high power (etching) and low power/off (passivation) states to dynamically balance stack layer etching progress with mask protection. This periodic action ensures adequate process margin by preventing excessive polymer deposition that would limit selectivity, while maintaining the ability to selectively etch the stack layer through controlled exposure during high power states
Solution Approach 2:
The patent changes RF power parameters through multiple discrete states to optimize both etching efficiency and mask protection. By implementing intermediate power states and varying duty cycles, the system achieves improved stack layer selectivity while maintaining adequate process margin, breaking the limitation where polymerizing species restrict both selectivity and process flexibility
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 effectively breaks the tradeoff between mask selectivity and clogging, allowing for precise control of critical dimensions and improved aspect ratio, reducing mask clogging risks while maintaining high selectivity and etch rate benefits.
Implementation Method 1
The no bias and low flux regime generates plasma that can reach to the top of mask and removes polymers deposited during the low level/off state on the top and neck area of the substrate
Implementation Method 2
The methods, described herein, control a mask etch rate while improving a tradeoff between selectivity and the process margin
Data Source
AI summary
A method for controlling a critical dimension of a mask layer is described. The method includes receiving a first primary parameter level, a second primary parameter level, a first secondary parameter level, a second secondary parameter level, and a third secondary parameter level. The method also includes generating a primary signal having the first primary parameter level, and transitioning the primary signal from the first primary parameter level to the second primary parameter level. The method further includes generating a secondary radio frequency (RF) signal having the first secondary parameter level, and transitioning the secondary RF signal from the first secondary parameter level to the second secondary parameter level. The method includes transitioning the secondary RF signal from the second secondary parameter level to the third secondary parameter level.