Buried Contact Structure for Low-Resistance Backside Power Delivery
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Solution Overview
Problem
Current semiconductor devices face challenges in reducing contact resistance between buried conductive structures and power delivery structures, which affects the efficiency of power delivery and device performance.
Innovation Solution
The semiconductor device design includes a buried conductive structure with a first contact plug and a first conductive barrier on its side surface, and a power delivery structure with a second contact plug and a second conductive barrier that extends to the bottom surface of the first contact plug, where the first conductive barrier is partially removed to reduce contact resistance, and the second conductive barrier is used to increase the contact area, enhancing electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive barrier is formed on the side surface of a contact plug to prevent metal diffusion, then device reliability is improved, but contact resistance increases due to the barrier layer blocking electrical contact
Solution Approach 1:
The conductive barrier layer is formed with non-uniform thickness: thicker at the upper portion of the contact plug side surface and thinner or absent at the lower portion. This local variation allows the upper part to prevent metal diffusion into the insulating liner (maintaining reliability) while the lower part maintains low contact resistance for electrical connection. The barrier layer's thickness transitions from blocking diffusion at the top to allowing electrical contact at the bottom.
Solution Approach 2:
The contact plug side surface is divided into two functional zones: an upper region with a conductive barrier layer for diffusion prevention, and a lower region with reduced or no barrier layer for electrical contact. This segmentation allows each zone to perform its specific function optimally - the upper zone ensures device reliability by blocking metal diffusion, while the lower zone minimizes contact resistance for power delivery.
2Reliability
If an insulating liner is formed around the contact plug to isolate metal diffusion, then device reliability is improved, but contact area is reduced due to the liner occupying space that could be conductive contact
Solution Approach 1:
The insulating liner is positioned to cover the upper portion of the contact plug where metal diffusion prevention is critical, while the lower portion near the substrate interface maintains direct metal-to-substrate contact. This local differentiation allows the liner to provide isolation where needed (upper region) while preserving maximum contact area (lower region).
Solution Approach 2:
The contact structure is segmented into an upper isolated region with the insulating liner for diffusion blocking, and a lower exposed region for electrical contact. The liner does not extend to the bottom of the contact plug, creating a segmented structure that simultaneously achieves both isolation and contact area objectives.
3Object-affected harmful factors
If the contact plug diameter is increased to reduce contact resistance, then electrical connectivity is improved, but device area and capacitance increase
Solution Approach 1:
The contact resistance is reduced not by increasing the contact plug diameter (which would increase device area), but by changing the electrical properties of the barrier layer. The barrier layer's thickness and conductivity are adjusted to maintain low contact resistance while keeping the contact plug dimensions small, thus reducing device area and parasitic capacitance.
Data Source
AI summary
A semiconductor device includes a substrate having a fin-type active pattern, source/drain regions on the fin-type active pattern, an interlayer insulating layer on the isolation insulating layer, and on the source/drain region, a contact structure electrically connected to the source/drain regions, a buried conductive structure electrically connected to the contact structure and buried in the interlayer insulating layer, and a power delivery structure that penetrates the substrate, and is in contact with a bottom surface of the buried conductive structure. The buried conductive structure includes a first contact plug, and a first conductive barrier on a side surface of the first contact plug and spaced apart from a bottom surface of the first contact plug. The power delivery structure includes a second contact plug in direct contact with the bottom surface of the first contact plug.