Dielectric-Fin FinFET SRAM Layout for Lower Contact Resistance
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Solution Overview
Problem
The challenge in FinFET fabrication is to maintain high circuit performance in SRAM cells while increasing fin density and decreasing fin geometry, which often results in increased source/drain contact resistance and coupling capacitance due to narrow fin-to-fin spacing, limiting the growth of source/drain epitaxial features and reducing landing area for contacts.
Innovation Solution
The introduction of dielectric fins between adjacent semiconductor fins to increase fin-to-fin spacing, allowing for greater growth of source/drain epitaxial features and enhancing the landing area for source/drain contacts, thereby reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fin geometry is decreased to increase fin density, then device density is improved, but source/drain contact resistance increases and coupling capacitance increases
Solution Approach 1:
A mandrel structure is introduced as an intermediary element between adjacent fins. The mandrel serves as a spacing maintainer that prevents direct interaction between source/drain regions of adjacent fins, thereby reducing coupling capacitance and improving contact resistance while allowing high fin density to be maintained
Solution Approach 2:
The mandrel structure is formed self-aligned to the fins through a single patterning process, eliminating the need for additional alignment steps. The mandrel automatically positions itself between adjacent fins during the deposition process, providing self-service spacing functionality
2Productivity
If fin-to-fin spacing is decreased to increase fin density, then device density is improved, but landing area for contacts is reduced
Solution Approach 1:
The mandrel acts as an intermediary structure that occupies the space between adjacent fins, effectively increasing the landing area available for source/drain contacts without increasing the overall device footprint. The mandrel provides a physical platform that enlarges the contact interface area
Solution Approach 2:
The mandrel structure adds a vertical dimension to the spacing mechanism, extending the spacing function into the third dimension. This allows horizontal fin density to be maintained while vertical mandrel height provides the additional spacing and landing area
Data Source
AI summary
An SRAM cell includes: first, second, third, fourth, and fifth dielectric fins disposed in this order along a first direction and oriented lengthwise along a second direction, where the first and the fifth dielectric fins define two edges of the SRAM cell; a first n-type semiconductor fin structure disposed between the first and the second dielectric fins; a second n-type semiconductor fin structure disposed between the fourth and the fifth dielectric fins; a first p-type semiconductor fin structure disposed between the second and the third dielectric fins; a second p-type semiconductor fin structure disposed between the third and the fourth dielectric fins, where each of the first and the second n-type semiconductor fin structures and each of the first and the second p-type semiconductor fin structures is oriented lengthwise along the second direction; and gate structures oriented lengthwise along the first direction, where the gate structures engage with one or more of the dielectric fin.