3D Stacked Semiconductor Contact Integration via Pitch Doubling
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Solution Overview
Problem
Contacting less than nominal pitch features between three-dimensional layers in semiconductor devices is challenging due to critical dimension and alignment constraints, limiting the effectiveness of pitch doubling and three-dimensional stacking techniques.
Innovation Solution
A semiconductor device structure and fabrication process that integrates nominal pitch contacts to connect less than nominal or nominal pitch features across multiple vertical stacking tiers, using techniques such as shallow trench isolation, tetraethyl orthosilicate layer formation, and chemical mechanical planarization to facilitate alignment and interconnect formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pitch doubling and three-dimensional stacking are used to increase device density, then device density increases, but contacting less than nominal pitch features becomes challenging due to critical dimension and alignment constraints
Solution Approach 1:
The patent segments the contact formation process into multiple discrete steps: forming mandrels at first pitch, depositing spacers to double the pitch, selectively removing portions, and forming contacts at the doubled pitch locations. This segmentation allows each step to be optimized independently, achieving nominal pitch contacts despite the overall pitch doubling strategy.
Solution Approach 2:
The patent performs preliminary actions by first forming the spacer layer and mandrels before final contact formation. The spacer hard mask is deposited and patterned in advance, creating a template that guides subsequent contact alignment. This preliminary structuring establishes the doubled pitch geometry before the actual contact fabrication begins.
2Quantity of substance
If less than nominal pitch features are used to increase device density, then device density increases, but critical dimension constraints worsen making contact formation difficult
Solution Approach 1:
The patent introduces an intermediary spacer layer that acts as a mediator between the nominal pitch mandrels and the final contact structures. This spacer hard mask serves as a temporary structure that defines the doubled pitch locations, allowing contacts to be formed at larger, more manufacturable dimensions while still achieving the density benefits of pitch doubling.
Solution Approach 2:
The patent changes the pitch parameter from the original sub-nominal pitch to a doubled nominal pitch through the spacer formation process. By transforming the pitch parameter, the contact features become large enough to meet critical dimension requirements while maintaining the increased device density achieved through the initial pitch doubling strategy.
3Quantity of substance
If multiple vertical stacking tiers are implemented to increase device density, then device density increases, but alignment constraints across layers become more severe
Solution Approach 1:
The patent creates equipotential alignment surfaces by forming planarized dielectric layers between stacking tiers. Each tier is built on a planar surface, ensuring that alignment references are at the same potential level across different layers. This approach simplifies alignment across multiple vertical tiers by providing consistent reference planes.
Solution Approach 2:
The patent resolves alignment constraints by transitioning from two-dimensional planar alignment to three-dimensional stacked alignment. The spacer-based pitch doubling creates vertical separation between contact levels, allowing independent optimization of alignment in each layer while maintaining overall inter-layer registration through the stacked architecture.
Data Source
AI summary
Briefly, in accordance with one or more embodiments, multilayer memory device, comprising a lower deck and an upper deck disposed on the lower deck, the decks comprising one or more memory cells coupled via one or more contacts. An isolation layer is disposed between the upper deck, and one or more contacts are formed between the upper deck and the lower deck to couple one or more of the contact lines of the upper deck with one or more contact lines of the lower deck.