Semiconductor Feature Patterning for Uniform Sub-Resolution Pitches
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving consistent and repeatable sub-resolution features with uniform pitch ratios due to limitations in photolithography technologies, particularly in forming features smaller than the achievable minimum size, which can lead to non-uniform asymmetrical pitches and increased complexity and cost with existing multi-patterning techniques.
Innovation Solution
A method involving multiple overcoat films and solubility-changing processes is employed to refine feature widths and pitches, using photolithography, anti-spacer processes, and acid diffusion to achieve target widths and uniform 1:1:1:1 line-space-line-space pitch ratios by modifying photoresist and overcoat structures through selective removal and deposition steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography is used to form features smaller than the achievable minimum size, then sub-resolution features can be created, but the features become non-uniform and asymmetrical with inconsistent pitch ratios
Solution Approach 1:
The patent segments the patterning process into multiple stages: first forming initial photoresist structures with relaxed pitch requirements, then using anti-spacer deposition and removal to create additional structures, and finally using acid diffusion to refine the pitch. This multi-stage segmentation allows each step to optimize for its specific function rather than attempting to achieve the final precision in a single lithography step.
Solution Approach 2:
The patent performs preliminary actions by first depositing the anti-spacer material and forming initial photoresist structures before attempting to achieve the final pitch ratio. The anti-spacer structures are formed in advance with controlled dimensions, and then selectively removed to create the desired pitch pattern. This preliminary structuring enables subsequent acid diffusion to act on pre-defined geometries, ensuring uniform results.
2Manufacturing precision
If existing multi-patterning techniques are used to achieve sub-resolution features, then feature density can be increased, but the process complexity and cost increase
Solution Approach 1:
The patent merges multiple functions into a unified process flow: the anti-spacer material serves both as a deposition layer for structure formation and as a sacrificial element for pitch definition. The acid diffusion process simultaneously refines both the photoresist structures and the pitch spacing in a single treatment step. This merging reduces the number of separate patterning cycles needed compared to traditional multi-patterning techniques.
Solution Approach 2:
The patent introduces an intermediary acid diffusion process that acts as a mediator between the lithography step and the final pattern formation. The acid diffuses through the anti-spacer material to modify the photoresist structures, enabling precise pitch control without requiring multiple lithography exposures. This intermediary chemical process simplifies the overall workflow by replacing complex sequential patterning steps.
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 allows for the formation of consistent sub-resolution features with targeted widths and pitches, reducing complexity and cost while maintaining high throughput, thereby addressing the limitations of existing photolithography technologies.
Implementation Method 1
depositing a first overcoat film on a semiconductor wafer that includes first patterned features of a photoresist layer
Implementation Method 2
baking the semiconductor wafer to form soluble portions of the first photoresist structures
Implementation Method 3
executing a solubility-changing process to cause the first overcoat structures to become insoluble for development
Implementation Method 4
developing the semiconductor wafer to remove portions of the second overcoat film to reveal and remove the soluble portions of the first photoresist structures
Implementation Method 5
depositing a third overcoat film that fills the second recesses and covers the second photoresist structures and the first overcoat structures
Implementation Method 6
baking the semiconductor wafer to form soluble portions of the first overcoat structures
Data Source
AI summary
In certain embodiments, a method includes forming, by photolithography on a semiconductor wafer, first patterned features (PFs) including first photoresist structures (PRSs) having a first width and first recesses having a second width less than the first width and greater than a target width; forming, via anti-spacer patterning processing, second PFs including second PRSs having a third width less than the first width, first overcoat structures (OCSs) of the second width interspersed between second PRSs, and second recesses having a fourth width less than the target width; and forming, via acid diffusion processing, third PFs including third PRSs having a fifth width, second OCSs of the target width interspersed between third PRSs, and third recesses defined by third PRSs and second OCSs and having a sixth width greater than the fourth width, portions of first OCSs having been selectively removed using the acid diffusion processing to form second OCSs.