Memory Fin Patterns via Multi-Line Etch Masks
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Solution Overview
Problem
Conventional lithographic techniques face challenges in achieving uniformity and fidelity for features smaller than 20 nm due to poor resolution and rough surfaces, particularly in creating sub-resolution lines and connections between them, which are beyond the capabilities of conventional photo-lithography systems.
Innovation Solution
A method involving a multi-line layer with alternating lines of materials with different etch resistivities, using multiple etch masks to selectively etch features, allowing for self-aligned cuts and fin creation independent of photolithographic registration, enabling the formation of high-resolution features and increasing pitch/feature density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithographic techniques are used, then the process is simple and straightforward, but the resolution and surface quality deteriorate for features smaller than 20 nm
Solution Approach 1:
The patterning process is divided into multiple discrete steps: forming mandrels with first pitch, depositing spacer material, anisotropically etching spacers, removing mandrels, and repeating the process. This segmentation allows each step to be optimized independently, achieving sub-20nm resolution through cumulative refinement rather than relying on a single lithographic exposure.
Solution Approach 2:
Mandrels are formed in advance as sacrificial structures that define the initial pitch. The spacer material is deposited conformally on these pre-formed mandrels before the mandrels are removed. This preliminary action establishes a framework that guides subsequent self-aligned patterning, ensuring precise feature placement without requiring high-resolution lithography at the final pitch.
Solution Approach 3:
The spacer structures are formed through self-aligned processes where the spacer material automatically conforms to the mandrel sidewalls. The anisotropic etching process selectively removes mandrels while preserving spacers based on directional etch rates. This self-service mechanism eliminates the need for additional alignment steps and photolithographic registration, achieving sub-lithographic pitch multiplication automatically.
2Length of moving object
If pitch multiplication techniques are used to increase feature density, then the feature pitch decreases, but the ability to make cuts and connections between lines deteriorates
Solution Approach 1:
The etch mask layer is selectively removed at specific locations to create cuts and connections. By applying local variations in the etch mask pattern, the process enables differential etching: areas with etch mask preserve spacers, while areas without etch mask allow spacer removal and underlying layer access. This local quality control maintains cut capability despite overall pitch reduction.
Solution Approach 2:
The process utilizes changes in etch direction (anisotropic vs. isotropic), material composition (different spacer and mandrel materials with distinct etch rates), and mask presence/absence to control feature formation. These parameter changes enable selective cut formation at any location within the pitch-multiplied pattern, maintaining manufacturing flexibility despite reduced feature pitch.
3Manufacturing precision
If multiple etch masks and material layers are used to achieve high resolution, then the manufacturing precision improves, but the process complexity increases
Solution Approach 1:
Multiple patterning functions are merged into a single self-aligned spacer formation process. The spacer material simultaneously serves as the pattern definition, the etch mask, and the structural element. This merging eliminates the need for separate alignment and exposure steps for each pattern layer, reducing process complexity while maintaining high pattern fidelity through self-aligned fabrication.
Solution Approach 2:
The process exploits parameter changes in material properties (etch selectivity, conformal deposition behavior, thermal stability) to achieve pattern transfer without requiring proportionally increasing process steps. By selecting materials with appropriate parameter differences, the process achieves high precision through material-driven self-organization rather than step-driven fabrication.
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 the creation of high-resolution features with improved process margins and increased pitch density, facilitating the fabrication of structures like memory arrays with sub-resolution dimensions, such as DRAM fin patterns, by leveraging differential etch resistivities and etch mask combinations.
Implementation Method 1
a multi-line layer is formed above a memorization layer on a substrate. The multi-line layer includes a region having a pattern of alternating lines of three materials that differ chemically from each other by having different etch resistivities relative to each other
Data Source
AI summary
Techniques disclosed herein, provide a method and fabrication structure for accurately increasing feature density for creating high-resolution features and also for cutting on pitch of sub-resolution features. Techniques include using multiple materials having different etch characteristics to selectively etch features and create cuts or blocks where specified. A multiline layer is formed of three or more different materials that provide differing etch characteristics. Etch masks, including interwoven etch masks, are used to selectively etch cuts within selected, exposed materials. Structures can then be cut and formed. Forming structures and cuts can be recorded in a memorization layer, which can also be used as an etch mask.