Pulsed Bias RF Etch for Ultra-High Aspect Ratio Dielectric
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Solution Overview
Problem
The challenge in semiconductor fabrication is the increasing aspect ratio of features during plasma etching, particularly for ultra-high density structures, which leads to twisting and distortion due to asymmetric etching and non-uniform fluorocarbon polymer deposition, affecting the ellipse ratio and feature alignment.
Innovation Solution
A method and apparatus for selectively etching ultra-high aspect ratio features using a carbon-based mask in an etch chamber, involving a flow of fluorocarbon and oxygen-containing molecules, with a pulsed bias RF signal to transform the etch gas into plasma, and a controller to manage the etch process, including selective removal of the fluorocarbon polymer to reshape the mask and reduce twisting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If continuous etching is performed to achieve high aspect ratio features, then etching depth increases, but twisting and distortion occur due to asymmetric etching and non-uniform polymer deposition
Solution Approach 1:
The patent applies periodic pulsing of the bias RF signal during the etching process. This creates alternating phases of polymer deposition and etching, which prevents asymmetric polymer accumulation and maintains uniform feature shapes throughout the etching depth, thereby achieving high aspect ratios without twisting or distortion
Solution Approach 2:
The patent dynamically changes the bias RF power parameter during etching by pulsing it between different power levels. This parameter modulation controls the polymer deposition rate and etching rate, ensuring uniform feature formation and preventing the asymmetric distortion that occurs with continuous etching
2Reliability
If fluorocarbon polymer is deposited to protect the mask during etching, then mask protection improves, but asymmetric deposition causes twisting and ellipse ratio changes
Solution Approach 1:
The patent uses periodic pulsing of the bias RF signal to create alternating deposition and etching phases. This ensures uniform polymer distribution on the mask and prevents asymmetric accumulation that would cause twisting and ellipse ratio changes, while still maintaining adequate mask protection
Solution Approach 2:
The patent maintains continuous polymer deposition throughout the etching process by pulsing rather than stopping. This continuous action ensures the mask remains protected while the periodic nature of the pulsing prevents asymmetric accumulation, thereby maintaining both mask protection and ellipse ratio control
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 effectively reduces twisting and maintains a controlled ellipse ratio, allowing for closer feature spacing and achieving high aspect ratios of up to 40:1, while ensuring precise etching of dielectric layers in semiconductor devices.
Implementation Method 1
An energizing RF signal is provided to transform the etch gas to a plasma
Implementation Method 2
A pulsed bias RF signal is provided
Data Source
AI summary
A method for selectively etching an ultra high aspect ratio feature dielectric layer through a carbon based mask in an etch chamber is provided. A flow of an etch gas is provided, comprising a fluorocarbon containing molecule and an oxygen containing molecule to the etch chamber. A pulsed bias RF signal is provided. An energizing RF signal is provided to transform the etch gas to a plasma.