Plasma Etching Method for Removing Scalloping in 3D NAND
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Solution Overview
Problem
Conventional plasma etching methods for laminated semiconductor memories, such as 3D-NAND flash memories, often create gaps or scalloping at the interface between silicon oxide and silicon nitride films due to differing etching speeds, leading to reduced reliability and degraded etching shapes, with existing methods only suppressing but not removing formed scalloping.
Innovation Solution
A plasma etching method involving two processes: the first uses a fluorine-containing and hydrogen-containing gas plasma to etch the laminated film, and the second uses a bromine-containing gas plasma to remove the unevenness formed at the interface between silicon-containing film layers, employing specific radio frequency powers and gas compositions to effectively flatten the scalloping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If plasma etching is performed using fluorine-containing gas to etch the laminated film, then the etching speed is improved, but unevenness (scalloping) is generated at the interface between silicon oxide and silicon nitride films
Solution Approach 1:
The etching process is divided into two separate steps: first using fluorine-containing gas (CF4/CHF3) to etch the laminated film at high speed, then using bromine-containing gas (HBr) to remove the generated scalloping. This segmentation allows each gas to perform its optimal function without compromise
Solution Approach 2:
The invention changes the chemical composition parameter of the etching gas from purely fluorine-containing to a two-stage process involving fluorine-containing gas followed by bromine-containing gas. This parameter change enables both high etching speed and smooth interface by utilizing the different chemical properties of the gases
2Device complexity
If conventional plasma etching methods are used, then the etching process is simple, but the scalloping generated cannot be removed
Solution Approach 1:
The etching process is divided into two separate steps: first using fluorine-containing gas (CF4/CHF3) to etch the laminated film at high speed, then using bromine-containing gas (HBr) to remove the generated scalloping. This segmentation allows each gas to perform its optimal function without compromise
Solution Approach 2:
The invention converts the harmful effect of scalloping generated during fluorine-based etching into a removable feature by introducing bromine-containing gas that specifically targets and eliminates the unevenness, transforming a process defect into an可控 (controllable) intermediate state
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 effectively removes scalloping at the interface between silicon oxide and silicon nitride films, enhancing the reliability and shape quality of the etched features by adjusting the etching speeds and using bromine-containing gases to sputter and deposit material, thereby improving the verticality and removability of the unevenness.
Implementation Method 1
generating a first plasma from a first processing gas that contains fluorine-containing gas and hydrogen-containing gas
Implementation Method 2
etch a laminated film including a first silicon-containing film layer and a second silicon-containing film layer with the generated first plasma
Implementation Method 3
generating a second plasma from a second processing gas that contains bromine-containing gas
Implementation Method 4
using bromine-containing gases to sputter and deposit material, thereby improving the verticality and removability of the unevenness
Data Source
AI summary
A plasma etching method includes a first process of generating a first plasma from a first processing gas that contains fluorine-containing gas and hydrogen-containing gas, by using a first radio frequency power, to etch a laminated film including a first silicon-containing film layer and a second silicon-containing film layer that is different from the first silicon-containing film layer, with the generated first plasma; and a second process that is performed after the first process and includes generating a second plasma from a second processing gas that contains bromine-containing gas, by using a second radio frequency power, to etch the laminated film with the generated second plasma. Unevenness is formed at an interface between the first silicon-containing film layer and the second silicon-containing film layer in the first process, and the unevenness is removed in the second process.