Resist Molecular Weight Gradient for Defect-Reduced Lithography
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Solution Overview
Problem
Lithography processes for advanced technology nodes, such as 14 nanometers and below, face challenges with bridge and blind defects due to insufficient developing contrast and line edge roughness in resist layers, particularly in negative tone development processes, which result in poor resist contrast and patterning fidelity.
Innovation Solution
The development of resist materials with a gradient of increasing weight-average molecular weight from the bottom to the top of the resist layer, utilizing a polymer with acid labile groups and cross-linkable functional groups, and a fluorine-containing cross-linker that floats to the surface, allowing for controlled cross-linking and reduced etch rates, thereby minimizing bridge and blind defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high soluble polymer is used as the resist layer, then the resist layer solubility is improved, but resist layer loss at non-exposed area occurs which induces bridge defect
Solution Approach 1:
The patent applies local quality by creating a molecular weight gradient within the resist layer, where the bottom portion has lower molecular weight (higher solubility) and the top portion has higher molecular weight (lower solubility). This spatial variation in molecular weight provides different solubility characteristics at different locations, allowing the bottom to dissolve properly while the top maintains structural integrity to prevent bridge defects.
2Strength
If a low soluble polymer is used as the resist layer, then the resist layer structural integrity is improved, but scum formation occurs and subsequent de-scum process induces bridge defect
Solution Approach 1:
The patent uses local quality by assigning different molecular weights to different portions of the resist layer. The top portion has higher molecular weight providing structural integrity to prevent scum formation, while the bottom portion has lower molecular weight enabling proper dissolution during development, thereby eliminating the need for de-scum processes that could cause bridge defects.
3Ease of manufacture
If uniform molecular weight resist layer is used, then the manufacturing process is simplified, but insufficient developing contrast and line edge roughness occur
Solution Approach 1:
The patent applies parameter changes by varying the molecular weight parameter across the resist layer thickness. The gradient in molecular weight creates different dissolution rates at different depths, providing the necessary developing contrast for high-resolution patterning while maintaining controlled line edge roughness, thus improving manufacturing precision without excessive process complexity.
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 enhances line width roughness and local critical dimension uniformity by reducing resist layer loss and scum formation, improving the quality of the resist pattern and subsequent IC device fabrication.
Implementation Method 1
a fluorine-containing cross-linker that floats to the surface
Implementation Method 2
utilizing a polymer with acid labile groups and cross-linkable functional groups, and a fluorine-containing cross-linker that floats to the surface, allowing for controlled cross-linking
Implementation Method 3
utilizing a polymer with acid labile groups and cross-linkable functional groups
Data Source
AI summary
A lithography method is described. The method includes forming a resist layer over a substrate, performing a treatment on the resist layer to form an upper portion of the resist layer having a first molecular weight and a lower portion of the resist layer having a second molecular weight less than the first molecular weight, performing an exposure process on the resist layer, and performing a developing process on the resist layer to form a patterned resist layer.