FinFET Gate Spacer Structure to Prevent S/D Gate Shorting
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Solution Overview
Problem
The semiconductor industry faces challenges in scaling down semiconductor devices like MOSFETs and finFETs, leading to increased complexity and the risk of electrical shorting due to the epitaxial source/drain regions extending into gate structures during fabrication.
Innovation Solution
The implementation of extended gate spacers with first and second spacer portions, where the first spacer portions protect the gate structures and the second spacer portions control the etch profiles of source/drain openings to prevent epitaxial source/drain regions from extending into gate structure regions, thereby maintaining device performance and manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gate spacers are used without extending below fin top surface, then manufacturing process is simpler, but epitaxial source/drain regions extend into gate structure regions causing electrical shorting
Solution Approach 1:
The gate spacer is divided into two distinct portions: a first spacer portion extending above the fin top surface to protect the gate structure during processing, and a second spacer portion extending below the fin top surface to control etch profiles and prevent source/drain region encroachment into the gate area. This segmentation allows each portion to fulfill specific functions that collectively prevent electrical shorting while maintaining manufacturing feasibility.
Solution Approach 2:
The gate spacer extends in the vertical dimension below the fin top surface, transitioning from a conventional two-dimensional planar structure to a three-dimensional structure with depth. This vertical extension into the subsurface region enables the spacer to control etch profiles and define source/drain region boundaries more effectively, preventing electrical shorting between source/drain regions and gate structures.
2Productivity
If device dimensions are scaled down to increase storage capacity and processing speed, then higher performance is achieved, but manufacturing complexity increases and electrical shorting risk increases
Solution Approach 1:
The extended gate spacer structure is formed in advance during the fabrication process, establishing precise geometric boundaries for source/drain regions before epitaxial growth occurs. The second spacer portion extending below the fin top surface pre-defines the etch profile, ensuring that source/drain regions are confined to appropriate regions and cannot encroach into gate structure areas, thereby preventing electrical shorting at scaled dimensions.
Solution Approach 2:
The gate spacer exhibits different properties and functions at different locations: the first spacer portion above the fin top surface provides gate structure protection and defines upper boundaries, while the second spacer portion below the fin top surface controls etch profiles and defines lower boundaries. This spatial differentiation of function allows precise control of source/drain region geometry at scaled dimensions without increasing overall manufacturing complexity.
3Reliability
If extended gate spacers are implemented to prevent electrical shorting, then device performance is maintained, but manufacturing process complexity increases
Solution Approach 1:
The formation of the extended gate spacer is merged with the existing fabrication process sequence, integrating the creation of both first and second spacer portions into standard processing steps. The gate spacer structure is formed using conventional deposition and etching techniques that are already part of the manufacturing workflow, allowing the extended structure to be implemented without requiring entirely new manufacturing equipment or processes.
Data Source
AI summary
A semiconductor device and methods of fabricating the same are disclosed. The semiconductor device includes a substrate, a fin structure with a fin top surface disposed on the substrate, a source/drain (S/D) region disposed on the fin structure, a gate structure disposed on the fin top surface, and a gate spacer with first and second spacer portions disposed between the gate structure and the S/D region. The first spacer portion extends above the fin top surface and is disposed along a sidewall of the gate structure. The second spacer portion extends below the fin top surface and is disposed along a sidewall of the S/D region.