Photoresist Patterning with Relief Pattern Misalignment Protection
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Solution Overview
Problem
Conventional lithographic techniques face challenges in achieving smaller feature sizes and pitch scaling due to overlay misalignment, particularly in double patterning methods like LELE and LLE, which suffer from poor throughput and defectivity.
Innovation Solution
The use of a photoresist layer with a solubility-shifting component that remains soluble to negative tone developers in 'shadowed' regions, even when exposed to actinic radiation, allowing for the creation of 'shadowed' regions in photoresist that prevent insolubility despite overlay misalignment, enabling successful pattern formation despite misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If double patterning methods (LELE or LLE) are used to achieve smaller feature sizes and pitch scaling, then feature size is reduced, but overlay misalignment occurs causing poor throughput and defectivity
Solution Approach 1:
The patent applies preliminary action by forming a first relief pattern that defines openings before the second lithographic exposure. These openings act as pre-positioned alignment references that guide the second pattern formation, ensuring that features are correctly positioned despite overlay misalignment. The relief pattern is created in advance to establish a framework for accurate subsequent patterning.
Solution Approach 2:
The patent implements feedback through the interaction between the first relief pattern and the second photoresist layer. The relief pattern provides physical feedback (topographic cues) that influence the deposition and development of the second photoresist, allowing the system to self-correct overlay misalignment. The pattern formation process uses the previously formed relief structures as feedback references to achieve precise final pattern placement.
2Length of moving object
If conventional lithographic techniques are used, then manufacturing process is simple, but feature size cannot be scaled down sufficiently
Solution Approach 1:
The patent applies segmentation by dividing the patterning process into distinct stages: first forming a relief pattern that defines openings, then depositing a second photoresist layer, followed by selective removal of photoresist from openings. This segmented approach enables pitch quartering and smaller feature sizes by breaking down the complex patterning task into manageable sequential steps, each optimized for specific functions.
Solution Approach 2:
The patent utilizes another dimension by introducing vertical relief patterns (topography) in addition to the planar photoresist layers. The first relief pattern creates height variations that serve as optical and physical references for the second lithographic step. This dimensional addition enables more precise pattern placement and facilitates advanced pitch scaling beyond conventional planar lithography limits.
3Manufacturing precision
If photoresist becomes insoluble in exposed regions, then pattern definition is achieved, but misalignment causes defects in shadowed regions
Solution Approach 1:
The patent applies local quality by creating regions with different solubility characteristics within the photoresist layer. The second photoresist layer has varying solubility depending on its location: regions over openings maintain high solubility to allow clearing and prevent defects, while other regions become insoluble to define the final pattern. This spatially differentiated solubility enables the system to simultaneously achieve pattern definition and misalignment tolerance.
Solution Approach 2:
The patent utilizes parameter changes by controlling the solubility parameter of the photoresist material through selective exposure and material composition. The second photoresist is formulated with solubility-shifting components that change its dissolution properties based on exposure conditions. By adjusting solubility parameters in different regions, the process achieves both precise pattern definition and robustness against overlay misalignment-induced defects.
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 ensures accurate formation of features like trenches and holes by maintaining solubility of photoresist in partially uncovered areas, preventing misalignment-induced defects and enabling continued shrinkage of semiconductor critical dimensions.
Implementation Method 1
openings having a width less than sufficient to enable wave propagation of electromagnetic radiation that has wavelengths greater than a predetermined threshold wavelength
Data Source
AI summary
Substrate patterning techniques herein protect against overlay misalignment. Techniques include using a combination of relief patterns in which one relief pattern includes openings filled with a particular photoresist and these openings have a width that is insufficient to enable wave propagation of electromagnetic radiation having wavelengths greater than a predetermined threshold wavelength. Accordingly, actinic radiation above a certain wavelength cannot affect the photoresist within these relatively small openings. Photoresist filled within these openings can be removed by specific developers with the openings partially uncovered, which helps ensure features and connections are fabricated as designed.