Plasma Etching Method for 3D NAND Step Shape Uniformity
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Solution Overview
Problem
In the manufacture of three-dimensional stacked semiconductor memory, such as 3D NAND flash memory, existing etching methods struggle to maintain high in-plane uniformity during the etching of multilayer films with step shapes, leading to potential electrical connectivity issues between metal wiring layers due to uneven etching rates across the step shape.
Innovation Solution
An etching method utilizing a plasma processing apparatus that alternately repeats etching processes with different silicon-containing films using specific processing gases, where the first silicon-containing film is etched with a fluorocarbon gas and the second with a hydrofluorocarbon gas, controlling RF power and pressure to ensure equal etching rates across flat and leading edge portions of the step shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used on multilayer films with step shapes, then the etching process can be completed, but in-plane uniformity deteriorates and shoulder cuts occur due to uneven etching rates across different regions
Solution Approach 1:
The etching process is segmented into multiple alternating etching steps, where different processing gases are used for different silicon-containing films (e.g., CF4 for SiO2, CHF3 for Si3N4). This segmentation allows independent optimization of etching parameters for each film type, achieving uniform etching rates across the entire multilayer structure and preventing shoulder cuts.
Solution Approach 2:
The patent employs periodic alternation between different etching processes targeting different film types. By repeating cycles of etching SiO2 films followed by etching Si3N4 films (or other silicon-containing films) a predetermined number of times, the method maintains consistent etching performance across all layers and prevents the formation of shoulder cuts that would compromise in-plane uniformity.
2Ease of operation
If single-gas etching is used for simplicity, then the process is easy to operate, but etching selectivity and precision deteriorate leading to shoulder cuts
Solution Approach 1:
The patent changes processing parameters (specifically processing gas type) based on the target film material. Different gases are selected to optimize etching rates and selectivity for different silicon-containing films, achieving precise control over etching uniformity while maintaining operational simplicity through automated parameter switching.
3Manufacturing precision
If alternating etching of different silicon-containing films is performed, then in-plane uniformity is improved, but process complexity increases
Solution Approach 1:
The patent employs a universal plasma processing apparatus capable of handling multiple processing gases and controlling various silicon-containing films. This multi-functional approach allows the same equipment to perform different etching operations by simply changing gas types and parameters, achieving high in-plane uniformity without requiring multiple specialized devices or excessively complex process infrastructure.
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 maintains high in-plane uniformity and prevents shoulder cuts, allowing for precise formation of step shapes that prevent electrical connectivity between adjacent metal wiring layers, thereby ensuring reliable semiconductor memory structure fabrication.
Implementation Method 1
etching the first silicon-containing film of the substrate by plasma of a first processing gas
Implementation Method 2
etching the first silicon-containing film by plasma of a first processing gas containing a fluorocarbon gas
Implementation Method 3
etching the second silicon-containing film by plasma of a second processing gas
Implementation Method 4
etching the second silicon-containing film by plasma of a second processing gas containing a hydrofluorocarbon gas
Data Source
AI summary
An etching method includes etching a first silicon-containing film of a substrate by plasma of a first processing gas; and etching a second silicon-containing film of the substrate by plasma of a second processing gas. The etching of the first silicon-containing film and the etching of the second silicon-containing film are repeated a preset number of times.