Alternating Plasma Etching for NAND Flash Memory Depth Uniformity
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Solution Overview
Problem
Existing etching methods for NAND type flash memory devices with three-dimensional structures struggle to achieve uniform depth and verticality of spaces in both regions with multi-layer films and single silicon oxide films when using hydrofluorocarbon gases, resulting in differences in etching rates and horizontal twisting of spaces.
Innovation Solution
An etching method involving alternating plasma generations of hydrofluorocarbon and fluorocarbon gases within a plasma processing apparatus, where the first gas preferentially etches the multi-layer film region and the second gas etches the single silicon oxide film region, with additional gases like nitrogen trifluoride, hydrogen, and carbonyl sulfide to enhance etching rates and verticality, and fluorocarbon deposition for protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a processing gas including a hydrofluorocarbon gas is used to etch both the first region with multi-layer film and the second region with single silicon oxide film, then both regions can be etched, but the etching rates differ causing depth difference and horizontal twisting of spaces
Solution Approach 1:
The etching process is segmented into multiple steps using different processing gases. The first processing gas (hydrofluorocarbon-based) selectively etches the multi-layer film region, while the second processing gas (fluorocarbon-based) etches the single silicon oxide film region. This segmentation allows each gas to optimize its etching action for specific regions, resolving the depth difference issue.
Solution Approach 2:
The patent changes the chemical composition parameters of the processing gas between steps. By switching from a hydrofluorocarbon-based gas to a fluorocarbon-based gas, the etching characteristics are adjusted to achieve uniform depth control across different regions while maintaining verticality of the formed spaces.
2Ease of manufacture
If a single processing gas is used for etching, then the process is simple, but it cannot achieve uniform etching depth and verticality across different region types
Solution Approach 1:
The etching process is divided into multiple sequential steps, each using a specifically designed processing gas. This segmentation enables precise control over etching depth and verticality for different region types, achieving high manufacturing precision despite the increased process complexity.
Solution Approach 2:
The patent systematically changes the chemical composition and flow rate parameters of the processing gas between etching steps. These parameter changes are optimized to achieve uniform etching depth and maintain verticality across both multi-layer film and single silicon oxide film regions.
3Productivity
If hydrofluorocarbon gas is used for etching, then both region types can be processed, but the etching rates are not uniform resulting in depth differences
Solution Approach 1:
The patent segments the etching process into two distinct phases: first using hydrofluorocarbon gas for the multi-layer film region, then using fluorocarbon gas for the single silicon oxide film region. This segmentation equalizes the etching rates across different regions by matching each gas to its optimal etching target.
Solution Approach 2:
The processing gas composition is changed from hydrofluorocarbon-based to fluorocarbon-based between steps. This parameter change adjusts the etching rate characteristics to achieve uniformity across different region types, resolving the depth difference problem while maintaining high productivity.
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 reduces the depth difference between the multi-layer and single silicon oxide film regions and improves the verticality of the formed spaces, ensuring precise and uniform etching for NAND flash memory manufacturing.
Implementation Method 1
generating plasma of a first processing gas including a hydrofluorocarbon gas within the processing container
Implementation Method 2
etching a first region including a multi-layer film formed by providing a silicon oxide film and a silicon nitride film alternately, and a second region having a single silicon oxide film
Implementation Method 3
generating plasma of a second processing gas including a fluorocarbon gas within the processing container
Implementation Method 4
etching a first region including a multi-layer film formed by providing a silicon oxide film and a silicon nitride film alternately, and a second region having a single silicon oxide film
Implementation Method 5
fluorocarbon deposition for protection
Data Source
AI summary
Disclosed is a method for etching a first region including a multi-layer film formed by providing silicon oxide films and silicon nitride films alternately, and a second region having a single silicon oxide film. The etching method includes: providing a processing target object including a mask provided on the first region and the second region within a processing container of a plasma processing apparatus; generating plasma of a first processing gas including a hydrofluorocarbon gas within the processing container that accommodates the processing target object; and generating plasma of a second processing gas including a fluorocarbon gas within the processing container that accommodates the processing target object. The step of generating the plasma of the first processing gas and the step of generating the plasma of the second processing gas are alternately repeated.