Low-Temperature Etching Gas Composition for 3D NAND Channel Holes
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Solution Overview
Problem
Current etching processes for NAND flash memory devices with three-dimensional structures face challenges in achieving high etch rates for oxide layers while maintaining selectivity for polysilicon layers at low temperatures, leading to incomplete channel hole formation and exposure of lower metal wirings due to differences in etch rates between oxide and nitride layers.
Innovation Solution
An etching gas composition including hydrogen, a halogen gas, a first gas with a phosphorus atom, and a second gas with a carbon atom and multiple different halogen atoms is used, which helps increase the etch rate for oxide layers and improve selectivity for polysilicon layers by controlling the flow rates of these gases, thereby optimizing the etching process in a low-temperature environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching gas is used to increase etch rate for oxide layers, then etch rate improves, but selectivity for polysilicon layers deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas by introducing a specific gas containing phosphorus atoms and controlling the flow rates of multiple gases (first gas, second gas, third gas) to achieve optimal etch rate and selectivity. This resolves the contradiction by adjusting gas composition parameters rather than using conventional fixed composition gases.
Solution Approach 2:
The patent uses a composite etching gas system comprising multiple gases working together: a first gas (containing phosphorus), a second gas (containing carbon and halogen atoms), and a third gas (hydrogen or halogen gas). This composite gas system achieves both high etch rate for oxide layers and maintained selectivity for polysilicon layers, resolving the trade-off between productivity and reliability.
2Reliability
If etching is performed at low temperature to maintain selectivity, then selectivity for polysilicon is maintained, but etch rate for oxide layer decreases
Solution Approach 1:
The patent changes the chemical reactivity parameters of the etching environment by introducing phosphorus-containing gas and controlling gas flow rates, enabling effective etching at low temperatures. This resolves the contradiction by modifying the chemical parameters of the etching process rather than relying on temperature alone.
Solution Approach 2:
The phosphorus-containing gas acts as an intermediary that enables the etching reaction to proceed effectively at low temperatures while maintaining selectivity. The specific gas composition mediates between the conflicting requirements of low temperature operation and high etch rate, allowing both selectivity and productivity to be achieved simultaneously.
3Productivity
If high etch rate is achieved for oxide layers, then channel hole formation is accelerated, but incomplete etching and exposure of lower metal wirings occur
Solution Approach 1:
The patent implements process control through monitoring and adjusting the flow rates of multiple gases (first gas, second gas, third gas) to achieve optimal etching results. This feedback mechanism ensures that high etch rates are maintained while preventing over-etching and exposure of lower metal wirings, thus resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The composite etching gas system with controlled composition ratios provides both high etch rate and precise control over etching depth and selectivity. The synergistic effect of multiple gases ensures complete channel hole formation without exposing lower metal wirings, resolving the contradiction between fast etching and precise manufacturing.
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 proposed etching gas composition enhances etch rates for oxide layers and maintains selectivity for polysilicon layers, preventing incomplete etching and exposure of lower metal wirings, thus ensuring effective channel hole formation and improved process efficiency in low-temperature environments.
Implementation Method 1
etching the other layer by generating plasma from an etching gas in the chamber
Data Source
AI summary
An etching gas and an etching method, the etching gas includes hydrogen gas; a halogen gas; a first gas; and a second gas, wherein the first gas includes a phosphorus atom, and the second gas includes a carbon atom and two or more halogen atoms that are different from each other.