Semiconductor Contact Plug Structure With Layered Dielectric Isolation
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Solution Overview
Problem
As semiconductor devices continue to integrate more components into a given area with reduced minimum feature sizes, challenges arise in reducing leakage between source/drain contact plugs and adjacent gate stacks, which affect electrical performance and etch and lithography process windows.
Innovation Solution
The formation of a plurality of dielectric layers over gate stacks during the manufacturing of semiconductor devices, specifically in FinFETs, to create source/drain contact plugs, which reduces leakage and improves electrical performance while enlarging etch and lithography process windows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If minimum feature sizes are reduced to increase integration density, then more components can be integrated into a given area, but leakage between source/drain contact plugs and adjacent gate stacks increases
Solution Approach 1:
An intermediate dielectric layer is introduced between the source/drain contact plugs and the adjacent gate stacks. This intermediate layer acts as a mediator that prevents direct electrical leakage while allowing the contact plugs to maintain their low-resistance electrical connection to the semiconductor regions. The dielectric material is specifically selected to provide adequate insulation properties.
Solution Approach 2:
The dielectric structure is segmented into multiple layers with different materials and properties. The first dielectric layer is positioned between the contact plug and the gate stack to prevent leakage, while additional dielectric layers provide structural support and electrical isolation. This segmentation allows optimization of each layer's thickness and material composition to address both leakage prevention and integration density requirements.
2Productivity
If minimum feature sizes are reduced to increase integration density, then more components can be integrated into a given area, but etch and lithography process windows decrease
Solution Approach 1:
The dielectric layers are designed with specific thickness parameters that are optimized for the reduced feature size geometry. By carefully controlling the thickness of the first dielectric layer (e.g., 5-50 nm) and subsequent layers, the structure maintains adequate electrical isolation while fitting within the constrained vertical space of miniaturized devices. This parameter optimization enables successful fabrication using standard etch and lithography processes even at reduced feature sizes.
Solution Approach 2:
Instead of horizontally expanding the distance between contact plugs and gate stacks (which would consume valuable planar area), the solution moves the isolation function to the vertical dimension by stacking multiple dielectric layers. This dimensional transition allows maintenance of lateral integration density while achieving the required electrical isolation through vertical layering, thereby preserving etch and lithography process windows.
3Reliability
If dielectric layers are added to reduce leakage, then electrical performance improves, but device complexity increases
Solution Approach 1:
The dielectric layers are applied locally only in the regions where leakage prevention is required - specifically between the source/drain contact plugs and adjacent gate stacks. Rather than uniformly increasing dielectric thickness across the entire device, the solution targets the specific problematic interfaces, thereby improving electrical performance with minimal additional complexity in non-critical regions.
Solution Approach 2:
The first dielectric layer serves as a specialized intermediary component that performs the specific function of leakage prevention at the contact plug-gate stack interface. This dedicated intermediate layer simplifies the overall design by concentrating the leakage prevention function in a single, well-defined structural element, making the complexity manageable and the electrical performance improvement targeted and measurable.
Data Source
AI summary
A semiconductor device a method of forming the same are provided. A semiconductor device includes a gate stack over a substrate. A first dielectric layer is over the gate stack. The first dielectric layer includes a first material. A second dielectric layer is over the first dielectric layer. The second dielectric layer includes a second material different from the first material. A first conductive feature is adjacent the gate stack. A second conductive feature is over and in physical contact with a topmost surface of the first conductive feature. A bottommost surface of the second conductive feature is in physical contact with a topmost surface of the second dielectric layer.