FinFET Source and Drain Contact Layout for Low Resistance and Capacitance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The shrinking gate pitch in semiconductor devices leads to contact-to-gate bridge concerns, resulting in increased contact resistance and capacitance, which are not adequately addressed by existing technologies, especially for FinFETs requiring narrow fin widths for short channel control.
Innovation Solution
The proposed solution involves designing semiconductor devices with specific contact structures, including circular and rectangular shaped contacts for drain and source nodes respectively, utilizing high-K dielectric layers and multiple metal materials to reduce contact resistance and capacitance, while maintaining high density and speed requirements for system-on-chip products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the gate pitch is shrunk to reduce device size, then device density is improved, but contact resistance and landing margin are degraded
Solution Approach 1:
The contact structure is segmented into multiple functional layers: a first contact layer directly contacting the source/drain region, a second contact layer overlying the first contact layer, and a third contact layer overlying the second contact layer. This multi-layer segmentation allows each layer to be optimized for specific functions, reducing overall contact resistance while maintaining compatibility with shrunk gate pitch dimensions.
Solution Approach 2:
The contact structure employs composite materials with different electrical and mechanical properties in each layer. The first contact layer uses materials optimized for interface contact with the source/drain region, while subsequent layers use materials optimized for vertical conduction and mechanical stability, creating a composite structure that overcomes the limitations of single-material contacts in scaled devices.
2Reliability
If the fin width is narrowed to improve short channel control, then transistor performance is improved, but top S/D region size is reduced leading to worse contact landing margin
Solution Approach 1:
The contact structure extends in the vertical dimension with multiple stacked layers, compensating for the reduced horizontal area of the S/D region. By adding vertical height through multiple contact layers, the effective contact area and volume are increased, providing sufficient landing margin even when the top S/D region area is constrained by narrow fin width.
Solution Approach 2:
The contact structure is divided into multiple layers that can be independently optimized. The lower layers provide a larger effective contact area with the S/D region, while upper layers provide mechanical support and electrical connection, allowing the narrow fin width to be maintained for short channel control while still achieving adequate contact dimensions through vertical segmentation.
3Reliability
If the contact layout is extended to improve contact resistance, then contact performance is improved, but area occupation and gate to contact capacitance are increased
Solution Approach 1:
Instead of extending the contact layout horizontally, which increases area occupation and gate-to-contact capacitance, the contact structure is extended vertically with multiple stacked layers. This vertical extension increases the effective contact volume and reduces contact resistance without increasing the horizontal footprint, thereby avoiding increased gate-to-contact capacitance and area occupation.
Data Source
AI summary
A semiconductor device includes a substrate, a semiconductor fin, a gate structure, a source structure, a drain structure, a source contact, and a drain contact. The semiconductor fin extends upwardly from the substrate. The gate structure extends across the semiconductor fin. The source structure is on the semiconductor fin. The drain structure is on the semiconductor fin, in which the source and drain structures are respectively on opposite sides of the gate structure in a plan view. The source contact lands on the source structure and forms a rectangular pattern in the plan view. The drain contact lands on the drain structure and forms a circular pattern in the plan view, in which the rectangular pattern of the source contact has a length greater than a longest dimension of the circular pattern of the drain contact.