Photoresist Hardening for Multi-Patterning Stress
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Solution Overview
Problem
The challenge in microfabrication is the complexity and cost associated with patterning at advanced technology nodes, particularly with self-aligned multi-patterning techniques, where photoresist mandrels deform due to compressive stress and lack precise control over critical dimensions, leading to issues with sidewall spacers and dimensional uniformity.
Innovation Solution
A method involving plasma-based deposition and curing of organic polymers on photoresist patterns to create a reverse taper profile, which hardens and strengthens the photoresist, allowing for straight sidewall spacers and precise dimensional control, reducing deformation and costs by eliminating the need for additional hardmask layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If photoresist mandrels are used for self-aligned multi-patterning, then cost is reduced by eliminating hardmask layers, but photoresist deforms under compressive stress from conformal coating
Solution Approach 1:
The photoresist mandrel is pre-hardened through exposure to UV or VUV light before the conformal coating process. This preliminary hardening action strengthens the photoresist structure in advance, enabling it to withstand the compressive stress of subsequent spacer material deposition without deforming or collapsing.
Solution Approach 2:
The mechanical properties of the photoresist mandrel are changed by controlling the hardening process parameters, including UV/VUV light exposure dose, wavelength, and atmospheric conditions. These parameter changes transform the photoresist from a soft, deformable state to a hardened, stress-resistant state that maintains structural integrity during multi-patterning operations.
2Stability of the object's composition
If conventional multi-patterning with hardmandrels is used, then structural stability is maintained, but manufacturing cost increases due to additional etch steps and sacrificial layers
Solution Approach 1:
The invention replaces expensive, permanent hardmask layers with a cheaper, temporary photoresist mandrel that is hardened for structural support during the patterning process. The photoresist serves as a disposable sacrificial structure that can be removed after transferring the pattern, eliminating the need for costly hardmandrels and reducing overall manufacturing expenses.
Solution Approach 2:
The hardened photoresist acts as an intermediary material between the lithographically defined pattern and the final etched structure. It provides the necessary mechanical support and dimensional stability during spacer deposition, then can be selectively removed, serving as a temporary mediator that enables the patterning process without requiring permanent hardmask layers.
3Device complexity
If photoresist mandrels are used without hardening, then process simplicity is maintained, but critical dimension control and line edge roughness deteriorate
Solution Approach 1:
The photoresist mandrel undergoes preliminary UV or VUV hardening treatment before being used as a spacer support structure. This pre-hardening action improves the dimensional stability and mechanical strength of the mandrel, enabling precise critical dimension control and reduced line edge roughness during the conformal coating and etching processes.
Solution Approach 2:
The physical and chemical parameters of the photoresist are changed through controlled hardening, including crosslinking density, glass transition temperature, and mechanical modulus. These parameter changes enhance the mandrel's ability to maintain precise critical dimensions and smooth line edges throughout the multi-patterning process.
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 accurate and cost-effective multi-patterning by maintaining mechanical integrity and dimensional precision of photoresist mandrels, reducing deformation and improving line edge roughness and critical dimension uniformity, thus facilitating advanced node fabrication without the need for expensive hardmask layers.
Implementation Method 1
A deposition process is executed that deposits an organic polymer on the first relief pattern. The deposition process includes a plasma-based deposition process
Implementation Method 2
The deposition process includes a plasma-based deposition process that includes a curing agent. The curing agent generates VUV (vacuum ultraviolet) light during plasma-based deposition
Data Source
AI summary
Techniques herein include methods of processing photoresist patterns and photoresist materials for successful use in multi-patterning operations. Techniques include combinations of targeted deposition, curing, and trimming to provide a post-processed resist that effectively enables multi-patterning using photoresist materials to function as mandrels. Photoresist patterns and mandrels are hardened, strengthened, and/or dimensionally adjusted to provide desired dimensions and/or mandrels enabling straight sidewall spacers. Polymer is deposited with tapered profile to compensate for compressive stresses of various conformal or subsequent films to result in a vertical profile despite any compression.