Reverse Tone Patterning Using Conformal Hard Mask and Protective Layer
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Solution Overview
Problem
Nanoimprint lithography faces challenges in achieving adequate planarization and etch selectivity, especially when pattern features have critical dimensions of 20 nm and below, particularly with non-uniformly sized features, leading to variability in critical dimensions and reduced effectiveness in reverse tone processes.
Innovation Solution
A method involving a conformal hard mask layer deposited by low-temperature atomic layer deposition, followed by a non-planar protective layer, which enhances critical dimension uniformity and etch selectivity, allowing for the creation of a relief pattern that is the inverse or reverse of an original pattern with non-uniformly-sized features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a planarized layer is formed over the solidified patterned layer to transfer the inverse pattern, then the reverse tone process can be performed, but adequate planarization cannot be achieved while retaining adequate etch selectivity, especially for features with critical dimensions of 20 nm and below
Solution Approach 1:
The patent divides the single planarized layer into two separate layers: a conformal hard mask layer and a non-planar protective layer. The conformal hard mask layer is deposited uniformly over the patterned layer to preserve critical dimension information, while the non-planar protective layer provides the necessary planarization for subsequent processing. This segmentation allows each layer to perform its specific function without compromising the other, solving the contradiction between maintaining etch selectivity and achieving planarization.
Solution Approach 2:
The conformal hard mask layer acts as an intermediary between the patterned layer and the non-planar protective layer. It transfers the pattern information from the solidified layer while being protected by the conformal coating, which then serves as a template for the inverse pattern transfer. This intermediary structure enables the reverse tone process to proceed with adequate planarization while preserving the necessary etch selectivity.
2Reliability
If a conformal hard mask layer is deposited by low temperature atomic layer deposition, then etch selectivity is improved, but the process complexity increases
Solution Approach 1:
The patent changes the deposition parameters by using low temperature atomic layer deposition (ALD) instead of conventional high temperature CVD. This parameter change enables the deposition of conformal hard mask layers with excellent step coverage and uniform thickness at temperatures below 100°C, which is crucial for maintaining the integrity of the underlying polymer pattern while achieving the required etch selectivity. The low temperature process prevents polymer degradation while providing the necessary film quality.
Solution Approach 2:
The patent replaces the conventional mechanical/thermal deposition process with a chemical vapor deposition process (ALD). Instead of relying on high temperature thermal fields, the low temperature ALD process uses controlled chemical reactions to deposit the conformal hard mask layer, providing better conformality and etch selectivity without the harmful thermal effects on the underlying pattern.
3Manufacturing precision
If the protective layer is made non-planar to preserve feature information, then etch selectivity is maintained, but planarization quality deteriorates
Solution Approach 1:
The patent segments the protective function into two distinct layers with different planarity characteristics. The conformal hard mask layer maintains perfect planarity relative to the underlying pattern, preserving all feature information. The non-planar protective layer sits on top and provides the necessary planarization for subsequent processing while allowing the conformal layer below to maintain the accurate pattern template. This segmentation resolves the contradiction by assigning different planarity requirements to different functional layers.
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 results in highly uniform critical dimensions of the reversed features, overcoming the limitations of planarization variability and etch selectivity issues in nanoimprint lithography, especially for features below 20 nm, by using silicon oxide or aluminum oxide as conformal hard masks and spin-on-glass or spin-on-carbon as protective layers.
Implementation Method 1
depositing a conformal hard mask layer by low temperature deposition (e.g., by atomic layer deposition (ALD))
Implementation Method 2
the non-planar protective layer is spin-on-glass (SOG)
Data Source
AI summary
Methods of reversing the tone of a pattern having non-uniformly sized features. The methods include depositing a highly conformal hard mask layer over the patterned layer with a non-planar protective coating and etch schemes for minimizing critical dimension variations.