Polysilicon Mask Silicon Deposit for Plasma Etching Precision
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Solution Overview
Problem
Conventional plasma etching methods experience decreased mask selectivity when using a polysilicon mask, leading to roughness issues and reduced etching precision.
Innovation Solution
A plasma etching method involving a deposition step where a silicon-containing deposit is applied using a negative DC voltage to a silicon upper electrode, followed by an etching step using a CF-based gas as a mask, improving mask selectivity and surface smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polysilicon mask is used in conventional plasma etching, then the etching process can be performed, but mask selectivity decreases leading to roughness issues and reduced etching precision
Solution Approach 1:
A silicon-containing deposit is deposited on the polysilicon mask surface before the etching process begins. This preliminary deposition modifies the mask surface properties, creating a more resistant layer that maintains mask selectivity during etching and prevents the roughness issues that would otherwise degrade etching precision.
Solution Approach 2:
The mask structure is transformed from a single-material polysilicon mask to a composite structure consisting of a polysilicon base layer with a silicon-containing deposit surface layer. This composite structure combines the advantages of both materials, maintaining the polysilicon's etching compatibility while adding the deposit's superior surface properties for enhanced selectivity and precision.
2Reliability
If a polysilicon mask is used without modification, then the process is simple, but mask selectivity decreases and surface smoothness is compromised
Solution Approach 1:
The silicon-containing deposit is deposited on the mask surface as a preliminary step before etching. This additional step, while increasing process complexity, is necessary to achieve the required mask selectivity and surface smoothness that cannot be obtained with a plain polysilicon mask alone.
3Productivity
If no deposit is applied to the mask, then the process is simpler and faster, but etching precision and line smoothness deteriorate
Solution Approach 1:
The silicon-containing deposit is applied in advance to the mask surface, creating a protective and precision-enhancing layer that allows for high-speed etching while maintaining excellent line smoothness and etching precision, resolving the trade-off between productivity and manufacturing precision.
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
The method enhances mask selectivity and etching precision by depositing a silicon-containing layer on the polysilicon mask, allowing for more vertical angles and smoother lines during etching, while maintaining high plasma resistance.
Implementation Method 1
a deposition step of depositing a silicon-containing deposit by a plasma of a processing gas while applying a negative DC voltage to an upper electrode made of silicon
Implementation Method 2
an etching step of etching the silicon oxide film by a plasma of a first CF-based gas while using as a mask the etching mask having the silicon-containing deposit deposited thereon
Data Source
AI summary
In a plasma etching method, with respect to a substrate to be processed, which has a base layer, a silicon oxide film, and an etching mask formed in this order, the etching mask having an etching pattern formed thereon and being formed of polysilicon, a silicon-containing deposit is deposited on a surface of the etching mask using a plasma generated from a processing gas, while applying a negative direct current voltage to an upper electrode formed of silicon. Furthermore, in the plasma etching method, the silicon oxide film is etched using plasma generated from a first CF-based gas using, as a mask, the etching mask having the silicon-containing deposit deposited thereon.