Self-Aligned Double Patterning for Precise Line Termini
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Solution Overview
Problem
Conventional photolithography techniques face limitations in resolving features below a critical dimension, leading to imperfect metal backfill due to misalignment of mask shapes, which results in acute corners and defects in self-aligned double patterning processes used in integrated circuit manufacturing.
Innovation Solution
The method involves forming a first and second hard mask layer, where the second mask layer is trimmed using photolithography to precisely determine the locations of line termini, allowing for closer spacing and consistent shape, enabling precise positioning and reducing defects by using the same lithographic mask for both trimming and mandrel formation in self-aligned double patterning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithography is used to form features, then the process is simple and direct, but the resolution is limited by critical dimension below which features cannot be resolved
Solution Approach 1:
The patent applies segmentation by dividing the patterning process into multiple stages: first forming mandrels at a relaxed pitch, then using spacer formation to create additional features. This self-aligned double patterning approach segments the original single-step photolithography into sequential steps, achieving sub-critical dimension features while managing process complexity through systematic breakdown of the patterning challenge
Solution Approach 2:
The patent transitions from two-dimensional planar patterning to three-dimensional structure formation by creating vertical spacers on mandrel sidewalls. This dimensional transition enables formation of features smaller than the photolithographic critical dimension, as the spacer thickness (controlled by deposition) becomes the limiting factor rather than optical resolution
2Reliability
If mask shapes are not precisely aligned, then the manufacturing process is simpler, but acute corners and defects occur in self-aligned double patterning
Solution Approach 1:
The patent implements self-service through self-aligned processes where the spacer formation automatically positions features relative to mandrels without requiring additional alignment steps. The mandrels serve as self-aligned templates that define spacer locations, eliminating the need for separate mask alignment operations and preventing acute corners through inherent geometric consistency
Solution Approach 2:
The patent applies preliminary action by first forming mandrels with precisely controlled shapes and positions before creating spacers. This preliminary mandrel formation establishes the geometric framework that prevents defects, as the mandrel dimensions and positions are predetermined to ensure proper spacer placement and avoid acute corner formation
3Manufacturing precision
If the distance between line termini is reduced, then the feature pitch is smaller and resolution is improved, but the minimum distance constraint is violated causing manufacturing issues
Solution Approach 1:
The patent changes the controlling parameter from photolithographic resolution (wavelength-limited) to deposition thickness (process-controlled). By forming spacers through atomic layer deposition or chemical vapor deposition, the feature dimensions are controlled by deposition parameters rather than optical parameters, enabling precise sub-critical dimension fabrication while maintaining manufacturability through well-established thin film processes
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 more precise placement of line termini, reducing the minimum distance between them and minimizing defects, thereby enhancing the resolution and accuracy in integrated circuit manufacturing beyond conventional photolithography limits.
Implementation Method 1
In conventional photolithography a photoresist is exposed to light through a mask. The photoresist is modified by the exposure in such a way that either the exposed or unexposed portions of the resist can be removed during subsequent development.
Implementation Method 2
A spacer formation process is then used to form spacers on the sides of the mandrel features.
Data Source
AI summary
The present disclosure, in some embodiments, relates to an integrated circuit structure. The integrated circuit structure includes a substrate and a hard mask over the substrate. The hard mask has sidewalls that form a first opening and a second opening exposing an upper surface of the substrate. A block mask is arranged on the hard mask and is set back from the sidewalls of the hard mask. Spacers are disposed over the block mask and have sidewalls that define a spacer opening exposing an upper surface of the block mask. The block mask extends from directly below the spacers to laterally past the sidewalls of the spacers.