Photoresist Underlayer Deposition for Sub-10 Nm EUV Patterning
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Solution Overview
Problem
Existing photoresist underlayers used in EUV lithography face challenges in achieving thicknesses less than 10 nm with uniformity and stability, leading to issues with etch selectivity and pattern quality as device feature sizes decrease.
Innovation Solution
The use of plasma-enhanced cyclic deposition methods, such as plasma-enhanced atomic layer deposition (PEALD) and plasma-enhanced chemical vapor deposition (PECVD), to form a photoresist underlayer with thicknesses less than 10 nm or 5 nm, utilizing precursors like dimethyldimethoxysilane and octamethylcyclotetrasiloxane, and post-deposition plasma treatments to achieve desired surface energy properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If spin-on glass (SOG) is deposited as a photoresist underlayer for EUV lithography, then the underlayer provides necessary support for pattern formation, but the thickness uniformity and adhesion are insufficient, particularly at thicknesses less than 10 nm
Solution Approach 1:
The patent changes the deposition parameters by transitioning from spin-coating to atomic layer deposition (ALD), enabling precise control of film thickness at the nanometer scale. ALD provides atomic-level thickness control and uniformity, resolving the contradiction between achieving thin underlayers (<10 nm) and maintaining thickness uniformity. The process parameters such as deposition temperature, precursor flow rates, and cycle numbers are optimized to achieve both thinness and uniformity while maintaining adhesion.
Solution Approach 2:
The patent employs a composite underlayer structure consisting of multiple materials deposited in sequence using ALD. The underlayer comprises a first material (e.g., silicon oxide) and a second material (e.g., silicon nitride or silicon oxynitride) with different properties. This composite structure provides both excellent adhesion to the substrate and uniform thickness control, while also offering appropriate etch selectivity for subsequent processing steps.
2Length of moving object
If the underlayer thickness is reduced to enable smaller feature formation, then the pitch resolution and aspect ratio improve, but the deposition difficulty and thickness non-uniformity increase
Solution Approach 1:
The patent replaces the mechanical spin-coating process with a chemical vapor deposition process (ALD). Spin-coating relies on mechanical centrifugal force which becomes difficult to control at very thin films, whereas ALD uses sequential chemical reactions in the vapor phase that naturally conform to substrate topography and provide uniform deposition even at thicknesses below 10 nm, enabling smaller feature sizes with maintained precision.
Solution Approach 2:
ALD employs periodic cyclic deposition where precursors are introduced in alternating pulses, allowing each layer to complete its reaction before the next precursor is introduced. This periodic action ensures complete surface coverage and uniform thickness buildup, even at extremely thin film dimensions, resolving the contradiction between reducing feature size and maintaining thickness uniformity.
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 solution provides a thin, uniform photoresist underlayer with improved etch selectivity, pattern quality, and stability, ensuring high pattern fidelity and compatibility with EUV lithography processes.
Implementation Method 1
forming a photoresist underlayer on a substrate. The photoresist underlayer can be formed using one or more of plasma-enhanced cyclic (e.g., atomic layer) deposition and plasma-enhanced chemical vapor deposition
Implementation Method 2
forming a photoresist underlayer on a substrate. The photoresist underlayer can be formed using one or more of plasma-enhanced cyclic (e.g., atomic layer) deposition and plasma-enhanced chemical vapor deposition
Implementation Method 3
In some cases, the photoresist underlayer can be exposed to a post-deposition treatment step that includes formation of a plasma
Data Source
AI summary
Methods of forming structures including a photoresist underlayer and structures including the photoresist underlayer are disclosed. Exemplary methods include forming the photoresist underlayer using one or more of plasma-enhanced cyclic (e.g., atomic layer) deposition and plasma-enhanced chemical vapor deposition. Surface properties of the photoresist underlayer can be manipulated using a treatment process.