Trench Isolation Structure for FinFET Bridging Prevention
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Solution Overview
Problem
In advanced semiconductor technology, the shrinking sizes of semiconductor devices lead to increased risk of epitaxial bridging between closely spaced fin segments and poor landing of source/drain contact plugs due to facet defects at the distal ends of fin segments, necessitating an improved isolation structure that can prevent these issues while achieving a smaller layout area.
Innovation Solution
A semiconductor structure featuring a trench with a first dielectric layer having a body portion, a protruding portion with a smaller width, and a shoulder portion, where a second dielectric layer covers the top corner of the trench, and a gate body covering the trench, formed using atomic layer deposition (ALD) with silicon nitride, to prevent epitaxial bridging and improve contact plug yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the width of trenches is scaled down to achieve smaller layout area, then the layout area is reduced, but the risk of epitaxial bridging between adjacent fin segments is increased
Solution Approach 1:
The isolation structure is segmented into three distinct portions: a body portion at the bottom, a protruding portion at the top with smaller width, and a shoulder portion connecting them. This segmentation allows the isolation structure to maintain electrical isolation functionality while reducing the top width to prevent epitaxial bridging between fin segments, thus resolving the contradiction between layout area reduction and bridging risk prevention.
Solution Approach 2:
The invention transitions from a conventional uniform-width trench structure to a three-dimensional isolation structure with varying width along its depth. The protruding portion extends upward with reduced width, creating a dimensional solution that prevents horizontal bridging while maintaining vertical isolation, thereby achieving both smaller layout area and reduced bridging risk.
2Area of stationary object
If the width of trenches is scaled down to achieve smaller layout area, then the layout area is reduced, but the facet defects at distal ends of fin segments increase resulting in poor contact plug landing
Solution Approach 1:
The isolation structure is divided into distinct portions with the protruding portion positioned at the top near the distal ends of fin segments. This segmentation creates a dedicated structure that prevents facet defects from forming at critical locations, ensuring proper contact plug landing while maintaining reduced layout area through the narrower top width.
Solution Approach 2:
The protruding portion of the isolation structure is formed in advance before epitaxial growth and contact plug formation. This preliminary structure prevents facet defects from developing at the distal ends of fin segments, ensuring that subsequent contact plug formation occurs on defect-free surfaces with proper landing precision.
3Manufacturing precision
If multiple-patterning processes are used to form finer fin structures, then the resolution and uniformity of fin structures are improved, but the number of process steps and manufacturing complexity increase
Solution Approach 1:
The isolation structure serves multiple functions: it provides electrical isolation between fin structures, prevents epitaxial bridging, and acts as a barrier to facet defect formation. By combining these functions into a single structure formed through integrated processes, the invention reduces the need for separate process steps that would otherwise be required, thereby managing manufacturing complexity while maintaining high fin structure uniformity.
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
The proposed structure effectively prevents epitaxial bridging between adjacent fin segments and enhances the yield of source/drain contact plugs by maintaining a smaller layout area and reducing facet defects, thereby improving the overall performance and reliability of semiconductor devices.
Implementation Method 1
formed using atomic layer deposition (ALD) with silicon nitride
Data Source
AI summary
The present invention provides a semiconductor structure including a fin structure formed on a substrate, and an isolation structure formed in the fin structure. The isolation structure includes a trench, and a first dielectric layer disposed in the trench wherein the first dielectric layer includes a body portion in the bottom, a protruding portion in the top with a top surface, and a shoulder portion connecting the body portion and the protruding portion. The protruding portion has a smaller width than the body portion. The semiconductor structure further includes a second dielectric layer covering a top corner of the trench and sandwiched between the protruding portion, the shoulder portion of the first dielectric layer and the upper sidewall of the trench.