Backside Contact Isolation Bars for Buried Power Rail Separation
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Solution Overview
Problem
The challenge in semiconductor devices is to form contacts that are properly isolated from each other and from surrounding conductive structures in high-density devices, where the reduction in device pitch makes it difficult to provide adequate isolation.
Innovation Solution
The use of dielectric isolation bars with tapered portions within contacts and buried power rail layers effectively isolates contacts and power rails, enabling electrical isolation even in reduced spacings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device pitch is reduced to increase areal density, then productivity and areal density improve, but isolation between contacts and active regions becomes difficult to provide
Solution Approach 1:
The patent introduces a vertical dimension to the isolation structure by forming dielectric isolation bars that extend through multiple layers (from the first interlevel dielectric layer through the second interlevel dielectric layer). This vertical extension allows adequate isolation between contacts and active regions even when horizontal spacing is reduced, effectively resolving the contradiction between reduced pitch and maintained isolation reliability
Solution Approach 2:
The dielectric isolation bar acts as an intermediary structure between contacts and active regions. It provides a physical and electrical barrier that prevents direct interaction between conductive elements, enabling proper isolation even in high-density configurations where traditional lateral isolation would be insufficient
2Productivity
If contact size is reduced due to smaller active regions, then areal density improves, but contacts can no longer be printed using lithographic processes
Solution Approach 1:
The patent compensates for reduced contact dimensions by extending the contact structure vertically through multiple dielectric layers. This allows the contact to maintain sufficient lithographic printability in the lateral dimension while achieving the required areal density through vertical integration and stacking
Solution Approach 2:
The contact structure is nested within multiple dielectric layers, with the contact extending vertically through the first and second interlevel dielectric layers. This nesting approach allows smaller lateral dimensions for higher density while maintaining manufacturability through the vertical configuration
Data Source
AI summary
A semiconductor device includes a dielectric isolation bar disposed in a region between an n-type active region and a p-type active region. The dielectric isolation bar has a first tapered portion disposed within a contact where the contact connects to the n-type active region or the p-type active region and a second tapered portion that cuts through portions of a buried power rail layer, wherein the dielectric isolation bar electrically isolates a lateral portion of the contact from surrounding structures and separates portions of the buried power rail layer.