Selective SiN Etch via Ion Suppression Filter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Plasma etching processes in semiconductor fabrication face challenges in precision control, leading to over-etching of shallow trenches and gaps, and unwanted reactions that affect material performance due to energetic plasma species.
Innovation Solution
An ion suppression element is positioned between the plasma and the substrate to reduce or eliminate ionically charged species, allowing more precise control of etch rate and selectivity by filtering the plasma to increase the concentration of fluorine radicals over ions, thereby enhancing the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional plasma etching is used to increase etch rate, then productivity is improved, but manufacturing precision deteriorates due to over-etching of shallow trenches and gaps
Solution Approach 1:
The plasma is segmented into different components (ions and radicals) and treated differently. The ion component is suppressed or filtered out, while the radical component is allowed to continue the etching process. This segmentation allows selective control over the etching mechanism to achieve both high rate and high precision
Solution Approach 2:
An intermediary element (ion suppression element or filter) is introduced between the plasma source and the substrate. This intermediary selectively removes or suppresses ions while allowing radicals to pass through, thereby mediating the interaction between plasma and substrate to achieve precise etching
2Productivity
If conventional plasma etching is used to enhance etching capability, then productivity is improved, but object-affected harmful factors increase due to unwanted reactions from energetic plasma species
Solution Approach 1:
The harmful ion component is extracted or removed from the plasma mixture before it reaches the substrate. By taking out the energetic ions that cause damage, only the beneficial radical species remain to perform the etching function, thus eliminating plasma damage while maintaining etching productivity
Solution Approach 2:
The plasma is processed to convert the potentially harmful energetic ions into a beneficial form by suppressing their energy or removing them, while retaining the useful radical species. This transforms the harmful plasma into a beneficial reactive gas that etches without causing damage
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 enables more precise control over the etching process, reducing plasma damage and improving etch selectivity, allowing for higher etch rates of specific materials like silicon nitride without affecting silicon oxide layers, thus enhancing the precision and reliability of semiconductor fabrication.
Implementation Method 1
applying energy to the fluorine-containing gas to generate a plasma in the plasma generation region. The plasma comprises fluorine radicals and fluorine ions
Implementation Method 2
filtering the plasma to provide a reactive gas having a higher concentration of fluorine radicals than fluorine ions
Implementation Method 3
The reactive gas etches the silicon nitride layer at a higher etch rate than the reactive gas etches the silicon oxide layer
Data Source
AI summary
A method of selectively etching silicon nitride from a substrate comprising a silicon nitride layer and a silicon oxide layer includes flowing a fluorine-containing gas into a plasma generation region of a substrate processing chamber and applying energy to the fluorine-containing gas to generate a plasma in the plasma generation region. The plasma comprises fluorine radicals and fluorine ions. The method also includes filtering the plasma to provide a reactive gas having a higher concentration of fluorine radicals than fluorine ions and flowing the reactive gas into a gas reaction region of the substrate processing chamber. The method also includes exposing the substrate to the reactive gas in the gas reaction region of the substrate processing chamber. The reactive gas etches the silicon nitride layer at a higher etch rate than the reactive gas etches the silicon oxide layer.