Boundary Trench Isolation With Conductive Barrier for Threshold Stability
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Solution Overview
Problem
As semiconductor devices scale down, the metal boundary effect (MBE) causes threshold voltage shifts due to metal diffusion between FETs with different work function stacks, degrading device performance by altering the effective work function and threshold voltage of adjacent transistors.
Innovation Solution
The implementation of a metal boundary trench isolation with an electrically conductive intermediate structure, comprising a capping layer, glue layer, and metal fill layer, is introduced to act as a diffusion barrier between work function stacks, preventing metal and contamination diffusion across the metal boundary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device dimensions are scaled down to increase storage capacity and processing speed, then productivity and performance are improved, but metal diffusion between adjacent FETs increases causing threshold voltage shifts and device performance degradation
Solution Approach 1:
A conductive intermediate structure is introduced between adjacent work function stacks to act as a diffusion barrier. This intermediary structure prevents metal atoms from diffusing across the metal boundary while maintaining electrical connectivity, thereby resolving the threshold voltage instability caused by metal diffusion during device scaling.
Solution Approach 2:
The metal boundary region is segmented by introducing a conductive intermediate structure that divides the continuous metal boundary into separate regions. This segmentation isolates the work function stacks from each other, preventing metal diffusion while allowing each FET to maintain its electrical functionality independently.
2Area of stationary object
If device dimensions are scaled down, then area occupancy is reduced, but metal and contamination diffusion across metal boundaries increases
Solution Approach 1:
The conductive intermediate structure serves as a mediator that blocks harmful metal and contamination diffusion between adjacent FETs. Despite the reduced device area, this intermediary structure effectively prevents contaminant transport across the metal boundary while maintaining the compact device layout.
Solution Approach 2:
The conductive intermediate structure functions as a thin film barrier that prevents metal and contamination diffusion. This thin film approach provides effective diffusion protection without occupying significant area, enabling compact device design while maintaining reliability.
3Productivity
If work function stacks are placed adjacent to each other to achieve higher device density, then productivity is improved, but metal diffusion alters the effective work function and degrades device performance
Solution Approach 1:
The conductive intermediate structure acts as a protective intermediary between adjacent work function stacks, preventing metal diffusion that would otherwise alter the effective work function. This allows high device density with maintained work function integrity and manufacturing precision.
Solution Approach 2:
The conductive intermediate structure is formed between work function stacks before subsequent metal deposition and processing steps. This preliminary action establishes a diffusion barrier in advance, preventing metal contamination and work function alteration during subsequent manufacturing processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively blocks metal diffusion and contamination, stabilizing the threshold voltage of FETs and enhancing device performance by maintaining the integrity of work function stacks, thereby improving the reliability and efficiency of semiconductor devices.
Implementation Method 1
an electrically conductive intermediate structure acting as a diffusion barrier between work function stacks
Implementation Method 2
preventing metal or contamination diffusion across the metal boundary
Data Source
AI summary
The present disclosure describes a semiconductor device having metal boundary trench isolation with electrically conductive intermediate structures acting as a metal diffusion barrier. The semiconductor structure includes a first fin structure and a second fin structure on a substrate, an insulating layer between the first and second fin structures, a gate dielectric layer on the insulating layer and the first and second fin structures, and a first work function stack and a second work function stack on the gate dielectric layer. The first work function stack is over the first fin structure and a first portion of the insulating layer, and the second work function stack is over the second fin structure and a second portion of the insulating layer adjacent to the first portion. The semiconductor structure further includes a conductive intermediate structure on the gate dielectric layer and between the first and second work function stacks.