Etching Oxide-Nitride Stacks Using C4F6H2 Plasma
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Solution Overview
Problem
The production of 3D NAND flash memory requires efficient and cost-effective etching of alternating oxide and nitride layers with high aspect ratios, which is challenging using conventional gas mixtures and processes, leading to increased processing costs and decreased efficiency.
Innovation Solution
A process using an optimized gas mixture that includes C4F6H2, which, when ionized, creates a plasma suitable for etching high aspect ratio features in a stack of alternating oxide and nitride layers, with additional gases like hydrogen-free fluorocarbons, argon, and oxygen to control etch rates and polymer generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional gas mixtures are used for etching alternating oxide and nitride layers, then the etching process can be performed, but the process becomes inefficient and costly with poor control over critical dimensions and aspect ratios
Solution Approach 1:
The patent applies parameter changes by optimizing the gas mixture composition with specific ratios of C4F6H2 (30-70%), CF4 (10-40%), and O2 (10-40%), along with adjusting RF power (50-200W) and pressure (1-10 mTorr) to achieve efficient etching of high aspect ratio features while maintaining process simplicity
2Manufacturing precision
If conventional gas mixtures are used for etching high aspect ratio features, then etching can be performed, but the critical dimensions and aspect ratios are not properly controlled
Solution Approach 1:
The patent achieves precise control of critical dimensions and aspect ratios by optimizing gas flow rates, pressure, and RF power parameters. The specific gas mixture composition and process conditions enable anisotropic etching that maintains vertical sidewalls and precise dimensional control while preserving high etching throughput
Solution Approach 2:
The patent uses oxygen (O2) as an intermediary gas that reacts with carbon-containing species to form CO and CO2, preventing polymer deposition on sidewalls and enabling better etch profile control and aspect ratio management while maintaining etching efficiency
3Device complexity
If a single etch process is used to etch both oxide and nitride layers, then process complexity is reduced, but selectivity between layers becomes difficult to control
Solution Approach 1:
The patent achieves selective etching of oxide and nitride layers within a single process by carefully balancing the gas mixture composition. The C4F6H2 and CF4 provide fluorine species for oxide etching, while the O2 component enables nitride etching through oxygen-containing radical reactions, with selectivity controlled by adjusting gas ratios and process parameters
Solution Approach 2:
The patent uses a composite gas mixture comprising multiple components (C4F6H2, CF4, O2) that work synergistically to provide different etching chemistries. The combination of fluorocarbon species for oxide removal and oxygen species for nitride removal enables selective dual-layer etching in a single process step
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 simplifies the etching process, reduces costs, and improves efficiency by enabling the creation of high aspect ratio features in a single etch process, with controlled selectivity and aspect ratios, enhancing the fabrication of 3D NAND structures.
Implementation Method 1
A process using an optimized gas mixture that includes C4F6H2, which, when ionized, creates a plasma suitable for etching high aspect ratio features
Implementation Method 2
A process using an optimized gas mixture that includes C4F6H2, which, when ionized, creates a plasma
Implementation Method 3
etching high aspect ratio features in a stack of alternating oxide and nitride layers
Data Source
AI summary
An article having alternating oxide layers and nitride layers is etched by an etch process. The etch process includes providing a first gas comprising C4F6H2 in a chamber of an etch reactor, ionizing the C4F6H2 containing gas to produce a plasma comprising a plurality of ions, and etching the article using the plurality of ions.