Ti/WNx/WSixNy Gate Stack for Low Resistance
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Solution Overview
Problem
The existing tungsten polysilicon gate structures face challenges with high sheet resistance and contact resistance, particularly when using the Ti/WN diffusion barrier structure, which limits the development of tungsten polysilicon gates due to increased sheet resistance and polysilicon depletion effects in PMOSFETs.
Innovation Solution
A semiconductor device with a gate stack structure incorporating a Ti/WNx/WSixNy intermediate structure, where a titanium layer, a nitrogen-containing tungsten layer, and a nitrogen-containing tungsten silicide layer are used to form a low-resistance and low-depletion barrier, reducing sheet resistance and contact resistance while preventing impurity out-diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ti/WN diffusion barrier structure is used in the tungsten polysilicon gate, then contact resistance between the tungsten layer and polysilicon layer is reduced, but sheet resistance increases significantly
Solution Approach 1:
The diffusion barrier structure is segmented into multiple functional layers: a Ti layer in direct contact with polysilicon to minimize contact resistance, followed by a WN layer to provide diffusion barrier functionality, and finally a W layer to ensure low sheet resistance. This segmentation allows each layer to optimize for its specific function without compromising overall performance.
Solution Approach 2:
The invention uses a composite structure combining Ti, WN, and W materials in a stacked configuration. Each material contributes its unique properties: Ti provides excellent contact with polysilicon, WN provides nitrogen diffusion barrier properties, and W provides low electrical resistance. The composite structure achieves properties that individual materials cannot provide alone.
2Reliability
If the Ti/WN structure is used to reduce contact resistance, then polysilicon depletion effect increases in PMOSFETs
Solution Approach 1:
The WN layer acts as an intermediary between the Ti layer and the polysilicon, preventing direct interaction that would cause polysilicon depletion. The W layer serves as another intermediary layer that mediates between the WN and the polysilicon contact interface. These intermediary layers reduce the harmful depletion effect while maintaining the low contact resistance benefit of the Ti layer.
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
The proposed structure achieves low contact resistance and sheet resistance, reduces polysilicon depletion, and enhances the performance of tungsten polysilicon gates by using a Ti/WNx/WSixNy intermediate structure, effectively addressing the limitations of the Ti/WN structure.
Implementation Method 1
a Ti/WNx/WSixNy intermediate structure, where a titanium layer, a nitrogen-containing tungsten layer, and a nitrogen-containing tungsten silicide layer are used to form a low-resistance and low-depletion barrier, reducing sheet resistance and contact resistance while preventing impurity out-diffusion
Data Source
AI summary
A semiconductor device includes a first conductive layer, a first intermediate structure over the first conductive layer, a second intermediate structure over the first intermediate structure, and a second conductive layer over the second intermediate structure. The first intermediate structure includes a metal silicide layer and a nitrogen containing metal layer. The second intermediate structure includes at least a nitrogen containing metal silicide layer.