Carbon Mask Protection Layer for Selective Plasma Etching
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Solution Overview
Problem
Existing etching processes face challenges with mask loss and reduced uniformity due to non-selective deposition of carbon-based materials, which degrade the etch profile and yield in semiconductor fabrication, particularly in high aspect ratio etching.
Innovation Solution
A method involving a pretreatment step to form C—O bonds on a patterned carbon-containing layer, followed by a reaction step with an oxygen-reactive precursor to selectively create a mask protection layer, and an etch step using plasma to etch the underlying layer with the carbon-containing layer as a mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon-based materials are deposited during the etching process to protect the mask, then mask protection is improved, but non-selective deposition occurs on all surfaces including the material being etched, working against the etching process
Solution Approach 1:
The patent applies preliminary action by performing a pretreatment step before the main etching process. This pretreatment step exposes the carbon-containing mask layer to oxygen to form C-O bonds at the mask surfaces, creating a chemically modified surface that will selectively react with oxygen-reactive precursors during the etch process. This preliminary chemical modification enables the mask protection layer to form only where needed (on the mask) rather than non-selectively on all surfaces.
Solution Approach 2:
The patent implements local quality by creating distinct chemical properties at different locations. The C-O bonds are formed specifically at the mask surfaces through the pretreatment step, creating a localized chemical signature. During the etch process, oxygen-reactive precursors then react selectively with these C-O bonds only at the mask locations, forming protection layers locally where required while leaving the underlying layer surfaces unaffected and reactive to the etchant.
2Reliability
If mask thickness is increased to reduce mask loss, then mask protection is improved, but patterning capabilities and attainable aspect ratio and critical dimension are negatively impacted
Solution Approach 1:
The patent applies parameter changes by modifying the chemical state of the mask surface rather than changing physical parameters like thickness. The pretreatment step changes the surface chemistry by forming C-O bonds, and the subsequent reaction with oxygen-reactive precursors creates a protection layer with controlled properties. This allows mask protection without increasing mask thickness, thereby preserving patterning capabilities and critical dimension control.
3Productivity
If high bias power is used during HAR etch to improve etching performance, then etching speed is improved, but mask loss is increased
Solution Approach 1:
The patent uses preliminary action by preparing the mask surface in advance through the oxygen exposure step that forms C-O bonds. This chemical preparation creates a protective interface before the high power etching begins, allowing the mask to withstand the aggressive etching conditions without excessive loss, thereby enabling high bias power operation without the usual penalty of increased mask loss.
Solution Approach 2:
The C-O bonds formed during pretreatment act as an intermediary between the mask and the etching environment. These bonds create a chemically distinct interface that preferentially reacts with oxygen-reactive precursors, forming a protection layer that mediates the interaction between the mask and the high power plasma, reducing direct damage to the mask while allowing aggressive etching of the underlying layer.
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 provides improved selectivity and etch resistance, reducing mask loss and enhancing uniformity, especially in hydrogen-, chlorine-, and fluorine-rich environments, thereby improving the yield and quality of semiconductor fabrication.
Implementation Method 1
exposing surfaces of a patterned carbon-containing layer to an oxygen-containing gas to form C—O bonds at the surfaces
Implementation Method 2
exposing the C—O bonds to an oxygen-reactive precursor to selectively form a mask protection layer on the surfaces of the patterned carbon-containing layer
Implementation Method 3
flowing an etchant gas and exciting plasma from the etchant gas to etch the underlying layer using the patterned carbon-containing layer as an etch mask
Data Source
AI summary
A method of etching an underlying layer includes performing a pretreatment step, a reaction step, and an etch step. The pretreatment step includes exposing surfaces of a patterned carbon-containing layer to oxygen to form C—O bonds at the surfaces with or without using plasma. The reaction step includes exposing the C—O bonds to an oxygen-reactive precursor to selectively form a mask protection layer on the surfaces of the patterned carbon-containing layer. The etch step is performed after the pretreatment step, and includes flowing an etchant gas and exciting plasma from the etchant gas to etch the underlying layer using the patterned carbon-containing layer as an etch mask. Any of the pretreatment step, the reaction step, and the etch step may be performed consecutively, concurrently, or repeated as a cycle.