U-Shaped Metal Gate Electrode Layout for Lower Contact Resistance
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Solution Overview
Problem
Conventional semiconductor devices face challenges in reducing gate contact resistance as they scale down, leading to suboptimal performance due to increased electrical resistance.
Innovation Solution
A novel metal gate electrode formation method where a fill-metal layer with a 'U-shaped' cross-sectional profile is formed before some work function metal layers, increasing surface contact area and reducing contact resistance, while also improving gap-filling performance by widening the trench to be filled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gate electrode structures are used in scaled-down devices, then manufacturing process remains simple, but gate contact resistance increases leading to suboptimal performance
Solution Approach 1:
The gate electrode is segmented into multiple distinct layers: a fill-metal layer (non-work function metal) and one or more work-function metal layers. This segmentation allows each layer to serve specific functions - the fill-metal provides low-resistance electrical contact while the work-function layers provide appropriate energy levels, thereby reducing gate contact resistance without requiring complete structural redesign
Solution Approach 2:
The fill-metal layer is deposited first before the work-function metal layers. This preliminary action creates a foundation layer that improves gap-filling performance and establishes a low-resistance pathway early in the fabrication process, making subsequent layer deposition easier and more effective
2Productivity
If device geometry is scaled down to increase functional density, then production efficiency increases, but electrical resistance becomes a greater concern
Solution Approach 1:
The gate electrode uses composite material structure combining different metal types with complementary properties. The fill-metal (e.g., tungsten, copper, aluminum) provides excellent electrical conductivity and low contact resistance, while the work-function metal layers (e.g., titanium nitride, tantalum nitride) provide appropriate energy levels for device operation. This composite approach maintains low electrical resistance even as device dimensions are scaled down to increase functional density
3Ease of manufacture
If fill-metal layer is deposited after work-function metal layers, then manufacturing sequence is simplified, but gap-filling performance deteriorates
Solution Approach 1:
The fill-metal layer is deposited in advance before the work-function metal layers. This preliminary deposition allows the fill-metal to properly fill the gate trench gaps and establish a solid foundation. When the work-function layers are subsequently deposited, they conformally coat the fill-metal surface, ensuring complete gap filling and proper material distribution throughout the gate electrode structure
Data Source
AI summary
A semiconductor device includes a channel component of a transistor and a gate component disposed over the channel component. The gate component includes: a dielectric layer, a first work function metal layer disposed over the dielectric layer, a fill-metal layer disposed over the first work function metal layer, and a second work function metal layer disposed over the fill-metal layer.