Buried Void Dielectric Isolation for IC Contact Reliability
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Solution Overview
Problem
As critical dimensions in integrated circuits (ICs) shrink, time-dependent dielectric breakdown (TDDB) becomes a significant reliability issue, leading to potential shorting of interconnects and IC defects due to dielectric layer destruction.
Innovation Solution
The formation of buried voids in the dielectric layer between contact plugs, which are partially filled with a dielectric filler to block communication paths and prevent shorting, while allowing contact plugs to be formed within the vias, thereby enhancing IC reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the dielectric layer is made thinner to reduce critical dimensions, then the IC size is reduced, but the reliability deteriorates due to time-dependent dielectric breakdown
Solution Approach 1:
The dielectric layer is segmented into multiple regions: a first dielectric region, a second dielectric region, and a buried void region between them. This segmentation allows each region to have different thicknesses and properties, enabling the overall structure to maintain smaller critical dimensions while preserving reliability through the thicker first dielectric region that provides enhanced TDDB resistance.
Solution Approach 2:
Different regions of the dielectric layer are assigned different local qualities: the first dielectric region has a greater thickness to provide high TDDB resistance, while the buried void region is positioned specifically between contact plugs to prevent shorting. This local differentiation allows the structure to simultaneously achieve small critical dimensions and high reliability.
2Manufacturing precision
If the dielectric layer thickness is reduced to shrink IC features, then the feature size is reduced, but the risk of dielectric breakdown increases
Solution Approach 1:
The dielectric layer is divided into a first dielectric region and a second dielectric region separated by a buried void. The first dielectric region maintains a greater thickness to prevent breakdown, while the overall feature size is reduced through the segmented structure and the presence of the buried void, achieving both small features and high breakdown resistance.
Solution Approach 2:
The buried void acts as an intermediary element between the first and second dielectric regions. It provides electrical isolation that prevents breakdown propagation, allowing the structure to achieve reduced feature sizes while maintaining high breakdown resistance through the insulating void region.
3Ease of manufacture
If contact plugs are formed in vias without buried voids, then the manufacturing process is simpler, but shorting between contact plugs may occur
Solution Approach 1:
The via structure is segmented into a first via containing a first contact plug and a second via containing a second contact plug, with a buried void positioned between them. This segmentation physically separates the contact plugs to prevent shorting while maintaining a relatively simple manufacturing process that builds upon standard via formation techniques.
Solution Approach 2:
The buried void serves as an intermediary isolation structure between adjacent contact plugs. It provides a simple yet effective electrical barrier that prevents shorting without requiring complex manufacturing steps, as the void can be formed through standard etching and filling processes.
Data Source
AI summary
A method for forming a device is disclosed. The method includes providing a substrate prepared with first and second contact regions and a dielectric layer over the contact region. First and second vias are formed in the dielectric layer. The first via is in communication with the first contact region and the second via is in communication with the second contact region. A buried void provides a communication path between the first and second vias. The vias and buried void are at least partially filled with a dielectric filler. The partially filled buried void blocks the communication path between the first and second vias created by the buried void. The dielectric filler in the vias is removed, leaving remaining dielectric filler in the buried void to block the communication path between the first and second vias and contact plugs are formed in the vias.