Amorphous Carbon Mask Opening via Cyclic Plasma Etching
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Solution Overview
Problem
In the formation of semiconductor devices, existing methods face challenges in effectively opening amorphous carbon layer masks below a hardmask, particularly in achieving precise etching of high aspect ratio memory holes with minimal defects and maintaining circularity of feature cross-sections.
Innovation Solution
A method involving multiple cycles of plasma processing phases, where an opening phase with an oxygen-containing gas etches features in the amorphous carbon layer mask, followed by a cleaning phase with a hydrogen, carbon, and halogen-containing gas to remove redeposited hardmask and form a carbon-based passivation layer, is used to open the amorphous carbon layer mask below a hardmask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-step opening process is used, then the process complexity is reduced, but the circularity of feature cross-sections and manufacturing precision deteriorate
Solution Approach 1:
The opening process is segmented into multiple distinct phases: an opening phase using oxygen-containing gas to etch the amorphous carbon layer, and a cleaning phase using hydrogen/carbon/halogen-containing gas to remove redeposited hardmask and form passivation. This segmentation allows each phase to be optimized independently, achieving high circularity and precision without excessive overall complexity.
Solution Approach 2:
The process employs periodic alternation between opening phase and cleaning phase, where the plasma is activated during opening phase to etch features, then deactivated during cleaning phase to allow passive formation of carbon-based passivation layer. This periodic action enables precise control over feature geometry and reduces bowing.
2Speed
If continuous plasma is used, then the etching speed is maintained, but redeposited hardmask accumulates and manufacturing precision deteriorates
Solution Approach 1:
The plasma is periodically activated and deactivated. During the opening phase, plasma is active to provide etching speed. During the cleaning phase, plasma is deactivated, allowing the carbon-based passivation layer to form and prevent hardmask redeposition. This periodic action maintains etching speed while preventing CD variance accumulation.
Solution Approach 2:
The redeposition of hardmask, which would normally be a harmful effect, is converted into a beneficial process. The cleaning phase gas composition (hydrogen, carbon, and halogen-containing) is specifically designed to remove redeposited hardmask and form a protective carbon-based passivation layer, turning the potential harm into a quality improvement mechanism.
3Productivity
If high power plasma is used, then the etching rate is improved, but bowing and manufacturing precision worsen
Solution Approach 1:
The process alternates between high-power opening phase (improving etching rate) and low-power cleaning phase (reducing bowing). During the cleaning phase, reduced power allows gentle formation of passivation layer without the high-energy bombardment that causes bowing, while still achieving effective hardmask removal.
Solution Approach 2:
The process dynamically changes plasma parameters between phases: during opening phase, high power and oxygen-containing gas provide high etching rate; during cleaning phase, power is reduced and gas composition changes to hydrogen/carbon/halogen-containing mix, which lowers the etching rate but prevents bowing and forms passivation.
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 enhances the circularity of feature cross-sections, reduces defects, and minimizes CD variance and bowing, allowing for more precise etching of high aspect ratio memory holes and improving the overall quality of semiconductor device fabrication.
Implementation Method 1
creating a plasma from the opening gas in the plasma processing chamber, wherein the plasma etches features in the amorphous carbon layer mask
Implementation Method 2
creating a plasma from the cleaning gas in the plasma processing chamber, wherein the plasma removes redeposited hardmask and deposits a carbon-based passivation layer
Data Source
AI summary
A method for opening an amorphous carbon layer mask below a hardmask is provided. The opening an amorphous carbon layer mask comprises performing one or more cycles, where each cycle comprises an amorphous carbon layer mask opening phase and a cleaning phase. The amorphous carbon layer mask opening phase comprises flowing an opening gas into a plasma processing chamber, wherein the opening gas comprises an oxygen containing component, creating a plasma from the opening gas, which etches features in the amorphous carbon layer mask, and stopping the flow of the opening gas. The cleaning phase comprises flowing a cleaning gas into the plasma processing chamber, wherein the cleaning gas comprises a hydrogen containing component, a carbon containing component, and a halogen containing component, creating a plasma from the cleaning gas; and stopping the flow of the cleaning gas into the plasma processing chamber.