Dry Etching Method Using Carbon Polymer Sidewall Protection
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Solution Overview
Problem
Conventional dry etching techniques for metal gate electrodes in semiconductor devices face issues such as side etching and unevenness of the polysilicon film sidewall, as well as residue formation from metallic substances during etching, due to accelerated reactions and inadequate protective films.
Innovation Solution
A method involving the formation of a carbon polymer protective film on the polysilicon film sidewall using plasma, followed by etching with halogen-containing plasma to prevent side etching and residue attachment, allowing for the removal of metallic substances with the protective film during an ashing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a metallic material is etched under conditions that improve volatility of reaction products, then etching speed is improved, but side etching and unevenness of polysilicon film sidewall occur
Solution Approach 1:
A protective film is formed on the polysilicon film sidewall before the metallic material etching process. This preliminary protective layer prevents the etching plasma from directly attacking the polysilicon sidewall, thereby maintaining sidewall uniformity while allowing aggressive etching conditions to be used for the metallic material.
Solution Approach 2:
The protective film acts as an intermediary layer between the etching plasma and the polysilicon film sidewall. It selectively protects the polysilicon from side etching while allowing the etching process to proceed on the metallic material, thus mediating between the conflicting requirements of etching speed and sidewall precision.
2Productivity
If halogen gas plasma is used to etch metallic material, then etching capability is improved, but metallic substances scatter and attach to polysilicon film sidewall as residues
Solution Approach 1:
The protective film serves as an intermediary barrier that captures scattered metallic substances during the halogen gas plasma etching process. Instead of metallic residues directly attaching to the polysilicon sidewall, they deposit on the protective film which can then be removed together with the metallic residues.
Solution Approach 2:
The protective film, which would normally be considered a contaminant or waste product, is actually beneficial as it captures and collects scattered metallic substances. This converts the harmful effect of metallic scattering into a manageable situation where residues are concentrated on the protective film for easy removal.
3Manufacturing precision
If plasma containing carbon is used to form protective film on polysilicon sidewall, then sidewall protection is achieved, but processing complexity increases
Solution Approach 1:
The protective film formation step using carbon-containing plasma is merged with the existing etching process flow. The protective film is formed in-situ before the metallic material etching, combining protection and etching operations into a coordinated sequence rather than separate processes.
Solution Approach 2:
The protective film formed by carbon-containing plasma is self-organizing and automatically conforms to the polysilicon sidewall geometry. The plasma deposition process naturally creates a uniform protective layer without requiring additional masking or complex alignment steps, allowing the material to protect itself.
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 prevents side etching and unevenness of the polysilicon film sidewall and allows for the simple removal of metallic residues with the carbon polymer protective film, resulting in improved etching precision and cleanliness.
Implementation Method 1
a protective film made of a carbon polymer is formed on a sidewall of the polysilicon film using plasma containing carbons
Implementation Method 2
a metallic material as a lower film is etched using plasma containing a halogen gas
Data Source
AI summary
After etching a polysilicon film, when a protective film made of a carbon polymer is formed on a sidewall of the polysilicon film using plasma containing carbons, a metallic material as a lower film is etched using plasma containing a halogen gas under an etching condition in which volatility is improved due to the rise in a wafer temperature or the low pressure of a processing pressure, thereby preventing a side etching and unevenness of a sidewall of the polysilicon film. Further, by using the protective film made of a carbon polymer, metallic substances scattered at the time of etching the metallic material are not directly attached to the polysilicon film, but can be simply removed along with the protective film made of a carbon polymer in an asking step.