Cobalt Source/Drain Contact Plug With Wider Fill Window
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Solution Overview
Problem
As semiconductor devices progress to smaller technology nodes, controlling source/drain series resistance becomes increasingly difficult due to increased current density, with existing copper plug technology struggling to meet aggressive contact resistance specifications, leading to potential degradation of saturation current by 40% or more.
Innovation Solution
The method involves forming a contact structure by depositing a dielectric barrier layer over a workpiece, recessing it to expose the source/drain feature, and then depositing a metal layer to form a metal nitride layer, which is etched back to create a source/drain contact plug with a cobalt portion extending through dielectric layers, utilizing photon-assisted implantation to form a silicide layer and improve metal fill window and overlay requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper plug technology is used in smaller technology nodes, then existing contact structures can be maintained, but contact resistance increases and saturation current degrades by 40% or more
Solution Approach 1:
The patent changes the material parameter from copper to cobalt for the contact plug, which fundamentally alters the electrical properties. Cobalt provides lower contact resistance and better performance at smaller technology nodes, directly resolving the contradiction between maintaining reliable contacts and preserving saturation current.
Solution Approach 2:
The contact structure uses a composite approach with cobalt as the primary contact material, potentially combined with other materials in multi-layer structures. This composite strategy allows optimization of both contact resistance and current carrying capability, addressing the limitations of pure copper plugs.
2Length of moving object
If contact plug size is reduced for smaller technology nodes, then device scaling is achieved, but controlling source/drain series resistance becomes much more difficult
Solution Approach 1:
By changing the material composition to cobalt, the patent alters the fundamental electrical parameters of the contact plug. This material parameter change enables better control of series resistance at reduced dimensions, as cobalt maintains lower resistance even when scaled down to smaller technology nodes.
Solution Approach 2:
The patent applies different materials with specific local properties to different regions of the contact structure. Cobalt is specifically used in the contact plug region where low resistance is critical, while other materials may be used in surrounding areas, allowing optimized performance at each location despite overall size reduction.
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
This approach reduces contact resistance and improves process tolerance by creating a wider upper portion of the contact plug, enhancing the metal fill window and relaxing overlay requirements, thus addressing the challenge of high series resistance in smaller technology nodes.
Implementation Method 1
depositing a metal layer to form a metal nitride layer
Implementation Method 2
utilizing photon-assisted implantation to form a silicide layer
Data Source
AI summary
The present disclosure provides embodiments of a semiconductor device. In one embodiment, the semiconductor device includes a gate structure, a source/drain feature adjacent the gate structure, a first dielectric layer over the source/drain feature, an etch stop layer over the gate structure and the first dielectric layer, a second dielectric layer over the etch stop layer, a source/drain contact that includes a first portion extending through the first dielectric layer and a second portion extending through the etch stop layer and the second dielectric layer, a metal silicide layer disposed between the second portion and etch stop layer, and a metal nitride layer disposed between the first portion and the first dielectric layer.