Air Gap Deep Trench Isolation for High-Voltage Leakage
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Solution Overview
Problem
Integrated circuits using shallow trench isolation (STI) regions suffer from leakage currents and low breakdown voltages, particularly for high-voltage devices, which lead to latch-ups.
Innovation Solution
The implementation of a deep trench isolation structure with air gaps, where deep trenches are formed in the semiconductor substrate and filled with an Inter-Layer Dielectric (ILD) that creates air gaps within the trenches, acting as an isolation structure to prevent junction formation between p-type and n-type regions and enhance breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shallow trench isolation (STI) regions are used to isolate active regions, then device isolation is achieved, but leakage currents occur at the junctions of p-type and n-type regions and breakdown voltages are low
Solution Approach 1:
The isolation structure is segmented into multiple components: deep trenches extending below the substrate surface, air gaps positioned at the substrate interface, and dielectric material filling the upper portions of the trenches. This segmentation creates multiple isolation barriers that collectively block leakage currents more effectively than a single continuous dielectric layer, while the air gaps specifically address the junction leakage problem between p-type and n-type regions
Solution Approach 2:
The isolation approach transitions from shallow horizontal isolation to deep vertical isolation by etching trenches that extend significantly below the substrate surface. This dimensional change allows the isolation structure to intercept leakage current paths at deeper levels where the electric field is more confined, thereby increasing breakdown voltage and preventing latch-up conditions
2Reliability
If deep trenches with air gaps are formed to reduce leakage currents and increase breakdown voltages, then isolation performance is improved, but manufacturing complexity increases
Solution Approach 1:
The air gaps are formed preliminary to final dielectric filling by first creating suspended structures through selective release of sacrificial layers. This preliminary action establishes the air gap geometry before the complex dielectric deposition process, allowing subsequent dielectric layers to be deposited conformally over the air gaps without requiring precise alignment or complex patterning steps
Solution Approach 2:
Sacrificial sacrificial layers are introduced as intermediary elements that temporarily occupy the space where air gaps will eventually form. These intermediary layers simplify the manufacturing process by providing a straightforward method to define air gap locations through standard lithography and release processes, avoiding the need for complex direct air gap formation techniques
Data Source
AI summary
A device includes a semiconductor substrate, a contact plug over the semiconductor substrate, and an Inter-Layer Dielectric (ILD) layer over the semiconductor substrate, with the contact plug being disposed in the ILD. An air gap is sealed by a portion of the ILD and the semiconductor substrate. The air gap forms a full air gap ring encircling a portion of the semiconductor substrate.