Synchronized RF Pulses for High Aspect Ratio Etching
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Solution Overview
Problem
The challenge in semiconductor manufacturing lies in reliably etching material layers with high aspect ratios for three-dimensional stacking of semiconductor chips, where poor process control leads to irregular structure profiles and line edge roughness, causing bowed, distorted, or twisted profiles due to the growth of etching by-products.
Innovation Solution
The method involves using synchronized RF pulses in a processing chamber, with specific power cycles to control the etching process, including pre-coating, etching, and post-coating phases, to maintain accurate profile control and feature transfer, employing multiple RF powers to manage the etching profile and feature dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional continuous RF etching is used, then etching speed is maintained, but etching by-products accumulate and block small openings causing irregular profiles
Solution Approach 1:
The patent applies periodic pulsed RF bias power to the substrate during etching, alternating between etching phases (bias power on) and cleaning phases (bias power off). This periodic action prevents by-product accumulation in high aspect ratio structures by periodically removing deposited materials, thereby maintaining profile control while sustaining etching speed through continuous plasma generation.
Solution Approach 2:
The etching process is segmented into distinct phases: etching phase with RF bias power applied, and cleaning phase with RF bias power removed. This segmentation allows the process to alternate between material removal and by-product elimination, resolving the contradiction between maintaining etching speed and preventing profile degradation from by-product accumulation.
2Productivity
If high RF bias power is applied continuously, then etching rate increases, but line edge roughness and profile distortion increase
Solution Approach 1:
By periodically pulsing the RF bias power rather than applying it continuously, the process achieves high etching rates during the 'on' phases while allowing relaxation and by-product removal during the 'off' phases. This prevents the cumulative damage to line edges that would occur with continuous high power application.
Solution Approach 2:
The RF bias power is dynamically modulated between on and off states during the etching process, allowing the system to adapt between aggressive etching conditions and gentle cleaning conditions. This dynamic control optimizes both etching rate and profile quality throughout the process.
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 precise etching of high aspect ratio features with improved line integrity and reduced by-product growth, resulting in accurate and reliable formation of small critical dimension structures, particularly beneficial for three-dimensional semiconductor chip stacking.
Implementation Method 1
applying a first RF source power at a first time point to the processing chamber to form a plasma in the gas mixture
Implementation Method 2
applying a first RF bias power at a second time point to the processing chamber to perform an etching process on the substrate
Data Source
AI summary
Embodiments of the present invention provide methods for etching a material layer using synchronized RF pulses. In one embodiment, a method includes providing a gas mixture into a processing chamber, applying a first RF source power at a first time point to the processing chamber to form a plasma in the gas mixture, applying a first RF bias power at a second time point to the processing chamber to perform an etching process on the substrate, turning off the first RF bias power at a third time point while continuously maintaining the first RF source power on from the first time point through the second and the third time points, and turning off the first RF source power at a fourth time point while continuously providing the gas mixture to the processing chamber from the first time point through the second, third and fourth time points.