Deep Trench Silicide Blocking for Planar STI Isolation
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Solution Overview
Problem
Deep trench structures in semiconductor devices face issues with unwanted silicidation at edges, leading to non-planar surfaces and potential electrical contact failures, especially in wide trenches, and narrow trenches require isolation to prevent undesired silicidation during transistor contact formation.
Innovation Solution
The implementation of a silicide blocking layer on the top surface of deep trench structures, specifically using nitrogen-containing dielectric materials like silicon nitride or silicon oxynitride, to prevent silicidation and ensure proper isolation, combined with a bilayer dielectric liner structure within the trenches to facilitate electrical isolation and reduce lateral diffusion of dopants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trench structures are formed in semiconductor devices, then electrical isolation between circuits is improved, but unwanted silicidation occurs at trench edges leading to non-planar surfaces and potential contact failures
Solution Approach 1:
A silicide blocking layer is introduced as an intermediary between the deep trench structure and the polysilicon fill material. This blocking layer prevents direct contact and unwanted silicidation reactions at the trench edges, maintaining surface planarity while preserving the electrical isolation function of the deep trench structure.
Solution Approach 2:
The silicide blocking layer is applied in advance before polysilicon deposition to preemptively prevent silicidation reactions. By establishing this protective barrier beforehand, the patent prevents the harmful silicidation effect before it can occur, ensuring planar surfaces and reliable electrical contacts.
2Productivity
If wide deep trenches are used, then circuit density is improved, but unwanted silicidation at edges increases leading to non-planar surfaces
Solution Approach 1:
The silicide blocking layer serves as a mediator that enables the use of wide deep trenches for increased circuit density without suffering from edge silicidation. The blocking layer is conformally deposited on the trench walls and bottom, providing uniform protection that maintains surface planarity even in wide trench structures.
3Manufacturing precision
If narrow deep trenches are used, then surface planarity is maintained, but isolation to prevent undesired silicidation during transistor contact formation is required
Solution Approach 1:
The silicide blocking layer provides multiple functions simultaneously: it prevents unwanted silicidation at trench edges, maintains surface planarity, and provides electrical isolation during transistor contact formation. This multi-functional approach simplifies the overall device structure by eliminating the need for separate isolation structures.
Data Source
AI summary
An electronic device includes a semiconductor substrate and a semiconductor surface layer having a first conductivity type, the semiconductor surface layer over the semiconductor substrate and having a top surface, a buried layer having an opposite second conductivity type between the semiconductor surface layer and the semiconductor substrate, a dielectric isolation layer that extends over and into the semiconductor surface layer, a deep trench structure that extends through the dielectric isolation layer into the semiconductor surface layer, and a silicide blocking layer on a top surface of the deep trench structure.