Cyclic Plasma Etching of Carbon Layers for Sidewall Passivation
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Solution Overview
Problem
Conventional plasma etching techniques for forming high aspect ratio features in carbon-containing layers often result in issues like bowing, side-wall roughness, and striation, particularly when etching amorphous carbon layers, due to poor passivation of sidewalls.
Innovation Solution
A cyclic etch process is employed in a plasma processing chamber, involving the formation of a passivation layer using a first gas containing boron, silicon, or aluminum, followed by purging with a hydrogen-containing or oxygen-containing gas, and exposure to a plasma generated from the second gas, which extends the recess vertically into the carbon-containing layer, with multiple cycles ensuring conformal and precise etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching techniques are used to etch carbon-containing layers, then the etching process can proceed, but bowing, side-wall roughness, and striation occur due to poor sidewall passivation
Solution Approach 1:
A passivation layer is formed on the sidewalls before the main etching process begins. This preliminary action of depositing the passivation layer prevents the sidewalls from being etched during the subsequent plasma etching step, thereby eliminating bowing, side-wall roughness, and striation while maintaining precise etching control
Solution Approach 2:
The passivation layer acts as an intermediary protective layer between the plasma etching process and the sidewalls of the recess. This intermediary layer absorbs the harmful effects of the plasma on the sidewalls while allowing the etching process to proceed vertically into the carbon-containing layer, resulting in smooth, bow-free sidewalls
2Reliability
If a passivation layer is formed using boron, silicon, or aluminum gas, then sidewall protection is improved, but the process complexity increases due to cyclic steps
Solution Approach 1:
The etching process employs periodic cyclic action, alternating between passivation layer formation and plasma etching steps. This periodic cycle allows the passivation layer to be formed, then removed or penetrated during etching, and reformed in subsequent cycles, achieving reliable sidewall protection while maintaining process control through repetition
Solution Approach 2:
The continuous etching process is segmented into discrete cyclic steps: passivation layer formation, plasma etching, and purging. This segmentation allows each step to be optimized independently and facilitates precise control of the overall etching process, managing complexity through structured breakdown
3Ease of manufacture
If plasma etching is performed without passivation, then the process is simpler, but high aspect ratio features cannot be achieved with good profile control
Solution Approach 1:
The passivation layer provides localized protection specifically at the sidewalls of the recess, while the bottom of the recess remains exposed to the plasma etching process. This local differentiation allows the sidewalls to maintain their profile control and smoothness while the etching proceeds vertically to create high aspect ratio features
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 method effectively mitigates bowing and side-wall roughness, achieving conformal and precise etching of high aspect ratio features by enhancing side-wall passivation, thereby improving the quality of the carbon mask and reducing etch rate compromise.
Implementation Method 1
forming a passivation layer by exposing the substrate to a first gas including boron, silicon, or aluminum without powering the plasma source, the first gas interacting with the carbon-containing layer to form the passivation layer
Implementation Method 2
exposing the substrate to a plasma generated from the second gas by powering the plasma source
Data Source
AI summary
A method for processing a substrate includes performing a cyclic process including a plurality of cycles, where the cyclic process includes: forming, in a plasma processing chamber, a passivation layer over sidewalls of a recess in a carbon-containing layer, by exposing the substrate to a first gas including boron, silicon, or aluminum, the carbon-containing layer being disposed over a substrate, purging the plasma processing chamber with a second gas including a hydrogen-containing gas, an oxygen-containing gas, or molecular nitrogen, and exposing the substrate to a plasma generated from the second gas, where each cycle of the plurality of cycles extends the recess vertically into the carbon-containing layer.