Local Interconnect Structure with Non-Eroded Contact Trenches
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Solution Overview
Problem
Conventional integrated circuit interconnect structures suffer from eroded contact trenches, leading to electrical shorting due to non-planar optical planarization layer surfaces and over-etched corners, which compromise the integrity of local metal layers and underlying contact levels.
Innovation Solution
A local interconnect structure is formed using a split damascene process that includes partially filling contact trenches with conductive material before depositing a masking layer, ensuring sharp ninety-degree corners and preventing erosion, thereby maintaining the uniformity of the optical planarization layer surface and eliminating eroded contact trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact trenches are formed through the dielectric layer to establish contact vias, then electrical connection between metal contacts and local metal layers is achieved, but the upper surface of the optical planarization layer becomes non-planar forming crater regions
Solution Approach 1:
The patent applies preliminary action by depositing a first fill material into the contact trenches before forming the optical planarization layer. This pre-filling step ensures that when the OPL is deposited, it forms a planar upper surface without crater regions, as the trenches are already occupied by conductive material that supports the OPL deposition process.
Solution Approach 2:
The first fill material acts as an intermediary substance between the contact trenches and the optical planarization layer. It fills the trenches and provides a foundation that enables the OPL to form a planar surface, mediating between the need for deep trenches (for electrical connection) and the need for surface planarity.
2Shape
If the optical planarization layer is deposited to fill contact trenches, then surface planarity is improved, but over-etched corners occur in subsequent local metal layers leading to eroded contact trenches
Solution Approach 1:
The patent performs preliminary action by forming a protective layer over the contact trenches before depositing the optical planarization layer. This protective layer prevents the OPL from directly filling the trenches in a way that causes over-etching, and maintains the integrity of the trench corners during subsequent processing steps.
Solution Approach 2:
The protective layer serves as a cushioning element that prevents harmful over-etching effects before they can occur. By placing this layer beforehand, the patent protects the contact trench corners from erosion during the OPL deposition and subsequent etching processes.
3Reliability
If contact trenches are deeply etched to reach semiconductor contact structures, then electrical connectivity is established, but eroded corners create short-circuit paths between metal layers and underlying contacts
Solution Approach 1:
The patent introduces a protective layer as an intermediary between the contact trenches and the subsequent processing steps. This layer prevents the formation of eroded corners that would create short-circuit paths, while still allowing the trenches to be deeply etched for proper electrical connectivity to the semiconductor contact structures.
Data Source
AI summary
A local interconnect structure includes a substrate having a dielectric layer and at least one semiconductor contact structure embedded in the dielectric layer. An electrically conductive material is deposited in a non-eroded contact trench that defines at least one electrically conducive contact via. The contact via extends from a first end that is flush with an upper surface of the dielectric layer to a second end that contacts the at one semiconductor contact structure. A local conductive material layer is formed in the dielectric layer and contacts the first end of the contact via. The non-eroded contact trench includes sharp upper corners formed at approximately ninety degrees with respect to the first end of the contact via.