Stepped Surface Formation for Multilevel Interconnect Structures
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Solution Overview
Problem
Current methods for forming multilevel metal interconnect structures in semiconductor devices are costly and complex, particularly in creating electrical contacts to multiple levels of conductive metal lines in high-density circuitry, such as 3D NAND stacked memory devices, where efficient and cost-effective manufacturing processes are needed to maintain wiring density and scalability.
Innovation Solution
A method involving the formation of a stack with alternating insulator and sacrificial material layers, where trenches are etched and laterally recessed to create stepped surfaces, allowing for the formation of dielectric pillars and horizontal fins, enabling the integration of electrically conductive via contacts and reducing processing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional methods are used to form electrical contacts to multiple levels of conductive metal lines, then wiring density and scalability are maintained, but manufacturing cost increases and processing complexity increases
Solution Approach 1:
The patent divides the formation of electrical contacts into multiple sequential etching stages, where each stage creates contacts to a specific depth level. The alternating first and second material layers are processed in segments, with trenches formed to different depths in different stages. This segmentation allows standard processing equipment to be used repeatedly rather than requiring complex single-step processes, thereby reducing manufacturing cost while maintaining contact integrity to multiple wiring levels.
Solution Approach 2:
The patent performs preliminary actions by forming the alternating stack of first and second material layers before creating the trenches. The sacrificial second material layers are prepared in advance, and the etching process selectively removes these pre-positioned layers to create the stepped trench structures. This preliminary arrangement of materials enables subsequent simple etching operations to automatically generate the complex multi-level contact structure, reducing overall processing complexity.
2Productivity
If the number of wiring levels is increased in high-density circuitry, then wiring density improves, but the number of processing steps increases
Solution Approach 1:
The alternating first and second material layers serve multiple functions: the first material layers form the structural matrix, the second material layers act as sacrificial elements for trench formation, and together they define the multi-level contact structure. This multi-functional design allows a single stacked structure to provide electrical contacts to numerous wiring levels simultaneously, achieving high wiring density without proportionally increasing the number of separate processing steps.
Solution Approach 2:
The etching process is self-organizing in that it automatically creates the appropriate stepped trench structures by selectively removing the second material layers. The alternating layer structure guides the etching depth and pattern formation without requiring external control for each individual level. The process self-adapts to create contacts at multiple depths based on the pre-formed layer alternation, thereby achieving high wiring density with minimal processing steps.
Data Source
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AI summary
A trench can be formed through a stack of alternating plurality of first material layers and second material layers. A dielectric material liner and a trench fill material portion can be formed in the trench. The dielectric material liner and portions of first material layer can be simultaneously etched to form laterally-extending cavities having level-dependent lateral extents. A set of stepped surfaces can be formed by removing unmasked portions of the second material layers. Alternately, an alternating sequence of processing steps including vertical etch processes and lateral recess processes can be employed to laterally recess second material layers and to form laterally-extending cavities having level-dependent lateral extents. Lateral cavities can be simultaneously formed in multiple levels such that levels having laterally-extending cavities of a same lateral extent are offset across multiple integrated cavities.