Plasma Etching Method Using Fluorocarbon Mass Ratio
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Solution Overview
Problem
The existing plasma etching methods, particularly atomic layer etching (ALE), face challenges in achieving high etching selectivity and efficiency due to longer processing times and difficulties in refining fine etching patterns, as they require switching between deposition and etching steps, which can lead to unintended etching of protective films.
Innovation Solution
A plasma etching method using a specific mass ratio of fluorine atoms to carbon atoms in the processing gases, with a range of 2.4 to 3.1, allowing for alternating deposition and etching steps, and employing a noble gas as a main component in the second processing gas to enhance etching selectivity and reduce processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the etching rate of the etching step is increased to shorten processing time, then processing time is reduced, but etching of protective film or non-processing target film occurs, reducing etching selectivity
Solution Approach 1:
The patent divides the conventional single-step plasma etching process into two distinct steps: a deposition step that forms a thin film on the substrate surface, and an etching step that removes material. This segmentation allows independent optimization of each step - the deposition step creates a controlled thin film layer that enables faster etching without compromising selectivity, while the etching step can proceed at higher rates because the deposited film controls the etching front and prevents damage to non-target areas.
Solution Approach 2:
The deposition step is performed as a preliminary action before the etching step. By depositing a thin film in advance during the deposition step, the substrate surface is prepared for the subsequent etching step. This preliminary film formation enables the etching step to proceed faster and more selectively, as the deposited material provides a controlled interface for etching reactions and protects underlying non-target structures.
2Manufacturing precision
If atomic layer etching is used to achieve atomic-level etching shape control, then etching precision is improved, but processing time increases due to alternating deposition and etching steps
Solution Approach 1:
The patent optimizes the deposition time and etching time parameters to achieve the best balance between precision and efficiency. By carefully controlling the duration and conditions of each step, the process achieves atomic-level etching shape control while minimizing the total processing time. The parameters are tuned so that the deposited thin film thickness and etching rate are optimized for both precision and productivity.
3Productivity
If conventional plasma etching is used with concurrent deposition and etching, then processing efficiency is maintained, but etching shape control precision is reduced
Solution Approach 1:
The patent segments the concurrent deposition and etching process into alternating distinct deposition steps and etching steps. This segmentation allows for precise control of the thin film formation and etching removal processes, enabling atomic-level etching shape control that was not achievable with concurrent processes, while maintaining reasonable processing efficiency through optimized step durations.
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 shortens processing time and improves the etching selectivity ratio, enabling more precise and efficient etching of target films while minimizing the etching of non-target films, thus achieving better pattern refinement.
Implementation Method 1
fluorocarbons, inert gases, oxygen and the like are used as processing gases, and a high-frequency electric field is applied to such processing gases to cause a glow discharge and generate plasma
Implementation Method 2
a high-frequency electric field is applied to such processing gases to cause a glow discharge and generate plasma
Implementation Method 3
a technique has been proposed (for example, refer to PTL 1) that can inhibit etching of a non-processing target in ALE by using an inert gas that is excited to a metastable state (also referred to as a 'metastable gas')
Implementation Method 4
a deposition step of depositing a thin film on a processing subject substrate
Data Source
AI summary
A plasma etching method includes: a deposition step of providing an atmosphere containing a first processing gas including at least one gas including either or both of a fluorine atom and a carbon atom and a second processing gas having a noble gas as a main component inside a processing vessel, and forming a thin film; and an etching step of providing an atmosphere containing at least the second processing gas inside the processing vessel and plasma etching a processing subject substrate. The deposition step and the etching step are switched between and implemented alternately. When an atmosphere containing the first processing gas and the second processing gas is provided inside the processing vessel in the deposition step, the atmosphere is configured to contain at least 2.4 times and not more than 3.1 times more fluorine atoms than carbon atoms by mass.