Alternating Plasma Etching for Wide Opening Carbon Deposition
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Solution Overview
Problem
In plasma etching, wide openings in a substrate can lead to the deposition of carbon-containing substances, causing the etching process to stop and reducing the etching rate, while the selectivity of the etching process with respect to the mask is compromised due to the lack of control over the additive gases.
Innovation Solution
A method involving alternating plasma etching processes using first and second processing gases, each containing fluorocarbon gases with specific ratios of carbon to fluorine atoms, and including an additive gas like NF3 or SF6, where the additive gas flow rate is lower than the fluorocarbon gas flow rate, to prevent etching stoppage and enhance selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma etching is performed using fluorocarbon gas to etch the film, then the etching rate is improved, but carbon-containing substances are deposited in wide openings causing etching stoppage
Solution Approach 1:
The patent applies periodic action by alternately performing first plasma etching (using fluorocarbon gas for high etching rate) and second plasma etching (using oxygen-containing gas to remove carbon deposits). This periodic switching prevents carbon-containing substance accumulation in wide openings while maintaining overall high etching productivity, resolving the contradiction between etching rate and etching continuity.
2Reliability
If additive gas is increased to prevent carbon deposition, then etching continuity is improved, but selectivity with respect to the mask deteriorates
Solution Approach 1:
Instead of continuously adding large amounts of additive gas that would reduce selectivity, the patent uses periodic action by switching between fluorocarbon-based plasma (for etching) and oxygen-based plasma (for carbon removal). This allows carbon deposition prevention without compromising mask selectivity, as the oxygen plasma is applied only during the second etching step when carbon removal is needed.
3Productivity
If fluorocarbon gas flow rate is increased to maintain etching rate, then productivity is improved, but carbon-containing substance deposition increases causing etching stoppage
Solution Approach 1:
The patent converts the harmful carbon deposition effect into a beneficial process by intentionally allowing carbon-containing substances to be deposited during the first plasma etching step, then systematically removing them during the second plasma etching step using oxygen-containing gas. This controlled approach transforms the harmful deposition into a manageable intermediate state that enables higher overall productivity.
Solution Approach 2:
The periodic alternation between fluorocarbon-based plasma (which generates carbon deposits but provides high etching rate) and oxygen-based plasma (which removes carbon deposits) allows the system to operate at high productivity while preventing harmful carbon accumulation. The rhythmic switching ensures carbon is removed before it can cause etching stoppage.
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 prevents the decrease in etching rate and stoppage of etching in wide openings, while maintaining high selectivity of the film etching process with respect to the mask, allowing for efficient pattern transfer in device manufacturing.
Implementation Method 1
plasma etching is used to transfer a pattern of a mask to a film
Implementation Method 2
The film of the substrate is a film capable of being etched by fluorine chemical species
Implementation Method 3
radio frequency power is supplied to a lower electrode of a substrate support that supports the substrate to attract ions to the substrate to etch the film
Implementation Method 4
radio frequency power is supplied to a lower electrode
Implementation Method 5
The first processing gas further includes an additive gas that is a source for nitrogen or sulfur and fluorine
Data Source
AI summary
In a disclosed method, etching a film by using plasma of a first processing gas and etching the film by using plasma of a second processing gas are alternately repeated. The first processing gas and the second processing gas each include a fluorocarbon gas. In etching the film by using the plasma of the first processing gas and etching the film by using the plasma of the second processing gas, radio frequency power is used to attract ions to the substrate. The first processing gas further includes an additive gas that is a source for nitrogen or sulfur and fluorine. In the first processing gas, the flow rate of the additive gas is smaller than the flow rate of the fluorocarbon gas.