Etching Method Using Noble Gas Plasma for 3D-NAND Selectivity
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Solution Overview
Problem
Existing etching methods for 3D-NAND flash memory structures face challenges in achieving high selectivity of the silicon oxide layer with respect to the tungsten layer and undercoat layers, leading to increased etching time and loss of the undercoat layer.
Innovation Solution
An etching method using a process gas containing fluorocarbon gas and a noble gas with higher ionization energy than Ar, such as He, is employed, which generates a plasma that reduces the momentum of ionized particles, resulting in a low sputter yield and formation of a protective film on the tungsten layer, thereby improving selectivity and reducing loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a plasma etching process is used to etch holes into silicon oxide layer, then the etching rate is improved, but the selectivity of silicon oxide layer with respect to tungsten layer and undercoat layer deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the process gas by introducing fluorocarbon gas (CF4, C4F8, or C4F6) combined with oxygen and nitrogen. This chemical parameter change enables selective etching of silicon oxide while protecting tungsten and undercoat layers through in-situ polymer film formation, resolving the selectivity problem while maintaining high etching rates
Solution Approach 2:
The patent introduces an intermediary protective mechanism where fluorocarbon-based polymer films are formed in-situ on the tungsten layer and undercoat layer surfaces during the etching process. These polymer films act as intermediaries that prevent direct plasma interaction with the protected layers, thereby maintaining selectivity while allowing rapid etching of the silicon oxide layer
2Manufacturing precision
If the etching time is extended to improve selectivity, then the selectivity is improved, but the loss of undercoat layer increases
Solution Approach 1:
The fluorocarbon-based polymer films formed during etching serve as protective intermediaries on the undercoat layer surface. These films prevent direct plasma damage to the undercoat layer, allowing extended etching times to achieve high selectivity without increasing undercoat layer loss
Solution Approach 2:
The patent changes the process gas composition to include fluorocarbon gases that decompose to form protective polymer films. This chemical parameter change creates a protective barrier that reduces physical and chemical damage to the undercoat layer, enabling longer etching durations with minimal material loss
3Manufacturing precision
If a protective film is formed on tungsten layer using high deposition property process, then the selectivity is improved, but the process complexity increases
Solution Approach 1:
The patent merges the protective film formation step with the main etching process by using fluorocarbon-based process gases that simultaneously etch silicon oxide and deposit protective polymer films on tungsten and undercoat layers. This consolidation eliminates separate process steps, reducing overall process complexity while maintaining high selectivity
Solution Approach 2:
The etching process itself generates the protective polymer films through in-situ decomposition of fluorocarbon gases. The process serves its own protection function without requiring external intervention or separate deposition steps, thereby simplifying the overall manufacturing process while achieving high selectivity
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 method maintains the etching rate of the silicon oxide layer while enhancing selectivity to the tungsten layer, reducing loss of the undercoat layer, and preventing clogging of holes, thus improving the etching profile and throughput.
Implementation Method 1
forming a plasma from the process gas in the process chamber, thereby causing the multilayered film to be etched
Implementation Method 2
momentum of an ionized particle of the first gas is less than momentum of an ionized particle of Ar gas
Data Source
AI summary
A method of etching a substrate, on which a multilayered film is formed, is provided. The multilayered film includes a silicon-containing insulating layer, an undercoat layer provided under the silicon-containing insulating layer, and a mask layer provided above the silicon-containing insulating layer. When the substrate is loaded into a process chamber, a process gas containing a fluorocarbon gas and a noble gas is supplied into the process chamber, and the multilayered film is etched by the plasma formed from the process gas. The noble gas contains a first gas having higher ionization energy than Ar gas, and momentum of an ionized particle of the first gas is less than momentum of an ionized particle of Ar gas.