Curved Contact Geometry for Lower-Resistance CMOS Interfaces
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Solution Overview
Problem
High resistance issues at the interface between contact to source and drain regions and trench silicide contacts in next-generation CMOS devices due to high resistivity metal nitride liners, limiting device performance.
Innovation Solution
Removing the high resistivity metal nitride liner and replacing it with a selective metal growth having lower resistance, forming a contact structure with increased surface area through recessing and selective deposition of cobalt or other metals to reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal nitride liner is used at the contact interface, then the contact structure provides good adhesion and protection, but the resistance becomes too high
Solution Approach 1:
The contact structure is divided into multiple segments: a first contact portion extending through the intralevel dielectric, a second contact portion with increased surface area, and a third contact portion encapsulating the second. This segmentation allows each portion to serve different functions - the first provides structural support, the second reduces resistance through increased area, and the third provides protection, collectively resolving the contradiction between adhesion and resistance.
Solution Approach 2:
The second contact portion features an exterior surface defined by a curvature, transitioning from a planar to a curved geometry. This dimensional change increases the surface area available for electrical contact without significantly increasing the footprint, thereby reducing contact resistance while maintaining the compact structure needed for advanced CMOS devices.
2Object-affected harmful factors
If the contact surface area is increased to reduce resistance, then the contact resistance decreases, but the device density and integration are compromised
Solution Approach 1:
The second contact portion utilizes a curved exterior surface that extends vertically and radially, increasing the effective surface area for electrical contact without proportionally increasing the horizontal footprint. This allows resistance reduction while maintaining compatibility with high-density device integration requirements.
Solution Approach 2:
The third contact portion encapsulates the second contact portion, creating a nested structure where the curved second portion is contained within the protective third portion. This nesting arrangement maximizes the contact surface area of the second portion while keeping the overall structure compact, resolving the contradiction between resistance reduction and area minimization.
Data Source
AI summary
A method of increasing the surface area of a contact to an electrical device that in one embodiment includes forming a contact stud extending through an intralevel dielectric layer to a component of the electrical device, and selectively forming a contact region on the contact stud. The selectively formed contact region has an exterior surface defined by a curvature and has a surface area that is greater than a surface area of the contact stud. An interlevel dielectric layer is formed on the intralevel dielectric layer, wherein an interlevel contact extends through the interlevel dielectric layer into direct contact with the selectively formed contact region.