Sub-Zero Dry Etching With Thionyl Chloride Self-Cleaning
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Solution Overview
Problem
Existing dry etching processes face challenges with etch byproduct accumulation on sidewalls, leading to clogging and reduced throughput due to the need for frequent flash processes, especially at sub-zero degree temperatures, which also affect etch profile quality.
Innovation Solution
Employing thionyl chloride as a process gas for dry etching that enables self-cleaning of etch byproducts by forming HCl to remove residues and create a passivation layer, reducing the need for flash processes and improving surface smoothness without additional passivation gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etching is performed at sub-zero temperatures, then etch profile quality is improved, but etch byproduct accumulation on sidewalls increases leading to clogging
Solution Approach 1:
The patent converts the harmful etch byproducts into beneficial cleaning action by introducing oxygen plasma. The oxygen reacts with carbon-based etch byproducts to form volatile CO and CO2 species that are pumped away, while the byproducts themselves facilitate sidewall passivation when used in controlled amounts during the etch process
Solution Approach 2:
The patent changes the chemical composition parameters of the etch plasma by introducing oxygen into the fluorocarbon-based process gas. This parameter change transforms the plasma chemistry to enable simultaneous etching with built-in sidewall cleaning and passivation, resolving the accumulation problem while maintaining sub-zero temperature benefits
2Reliability
If flash processes are performed frequently to remove etch byproducts, then sidewall clogging is reduced, but throughput decreases
Solution Approach 1:
The patent implements continuous sidewall cleaning during the etch process itself by maintaining oxygen in the plasma throughout the etching operation. This continuous action eliminates the need for intermittent flash processes, as cleaning occurs simultaneously with material removal, thereby maintaining throughput while ensuring sidewall cleanliness
Solution Approach 2:
The etch process itself performs the cleaning function through in-situ oxygen plasma generation. The system uses its own operational parameters to automatically remove byproducts during etching, making the process self-cleaning and eliminating the need for separate dedicated cleaning steps that would reduce throughput
3Reliability
If additional passivation gases are introduced to prevent byproduct accumulation, then sidewall protection is improved, but process complexity increases
Solution Approach 1:
The patent makes the oxygen plasma serve multiple functions simultaneously: it acts as an etch gas to remove material, a cleaning agent to remove carbon byproducts, and a passivation source to protect sidewalls. This multi-functionality eliminates the need for separate dedicated passivation gases, maintaining process simplicity while achieving comprehensive sidewall protection
Solution Approach 2:
The patent merges the cleaning and passivation functions into the primary etch process by introducing oxygen into the fluorocarbon plasma. This combination creates a unified process where etching, cleaning, and passivation occur simultaneously using a single gas mixture, reducing process complexity compared to using multiple separate gases for each function
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
Achieves efficient dry etching with reduced etch byproduct accumulation, enhancing throughput and etch profile quality by minimizing flash processes and maintaining surface smoothness at sub-zero degree temperatures.
Implementation Method 1
Employing thionyl chloride as a process gas for dry etching that enables self-cleaning of etch byproducts by forming HCl to remove residues and create a passivation layer
Implementation Method 2
The etch chamber is configured to dry etch the target layer at a sub-zero degree Celsius temperature using the thionyl chloride delivered by the showerhead
Data Source
AI summary
An etch chamber includes a substrate support assembly for holding a base structure, and a showerhead comprising a plurality of gas delivery holes for delivering thionyl chloride. The etch chamber is configured to dry etch a target layer of the base structure at a sub-zero degree Celsius temperature using the thionyl chloride delivered by the showerhead in order to obtain a processed base structure. The processed base structure includes a plurality of features and a plurality of openings defined by an etch mask disposed on the target layer.