Bilayer Conductive Feature Reducing Contact Resistance in Semiconductor Trenches
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The semiconductor industry faces challenges in scaling planar devices, such as MOSFETs, due to issues like short-channel effects, current leakage, and interconnect structure resistance, particularly in high-mobility channel materials like silicon germanium alloys, where conventional conductive features face challenges with high contact resistance and metal filling defects.
Innovation Solution
A semiconductor device structure and method are proposed, featuring a bilayer conductive feature with a barrier-free bottom metal layer for enhanced gap filling and a top metal layer with higher conductivity, separated by a collective barrier layer, which reduces contact resistance and improves adhesion and barrier effects in the interconnect structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer conductive feature with barrier layer is used, then adhesion and barrier effects are provided, but contact resistance increases and gap filling becomes difficult
Solution Approach 1:
The conductive feature is divided into multiple metal layers (first metal layer, second metal layer, third metal layer) with different functions. The first metal layer provides gap filling, the second metal layer provides high conductivity, and the third metal layer provides adhesion and barrier effects. This segmentation allows each layer to be optimized for its specific function, resolving the contradiction between reliability and complexity.
Solution Approach 2:
The conductive feature uses a composite structure with multiple metal materials having different properties. Each metal layer is selected for its specific characteristics (filling capability, conductivity, adhesion), creating a composite system that achieves overall performance superior to single-material solutions, thereby improving reliability without excessive complexity.
2Productivity
If the dimensions of conductive features are reduced for scaling, then interconnect density increases, but contact resistance and metal filling defects increase
Solution Approach 1:
Different metal layers are assigned different local qualities suited to their specific roles. The first metal layer has high filling capability for narrow trenches, the second metal layer has high conductivity for signal transmission, and the third metal layer has strong adhesion. This local optimization allows small dimensions to be maintained while filling quality and electrical performance are improved.
3Reliability
If a barrier layer is added to prevent metal diffusion, then adhesion is improved, but contact resistance and gap filling challenges worsen
Solution Approach 1:
The barrier function is segmented from the filling function. The first metal layer (without barrier) provides gap filling, while the third metal layer (with adhesion/promoter layer) provides barrier effects. This segmentation allows gap filling to occur without barrier interference, then barrier effects are applied in subsequent layers, resolving the contradiction between adhesion and gap filling.
4Speed
If high-mobility channel materials like silicon germanium are used, then transistor performance improves, but interconnect resistance and contact resistance become more significant challenges
Solution Approach 1:
The interconnect structure uses composite metal materials to match the high-performance requirements enabled by high-mobility channels. The multi-layer metal structure with different conductivities and properties provides overall interconnect performance that complements the high-speed transistor channel, ensuring that interconnect resistance does not become the limiting factor, thus maintaining the benefits of high carrier mobility.
Data Source
AI summary
The present disclosure provides a method of forming a semiconductor device structure. The method includes forming a trench in a dielectric layer on a semiconductor substrate; forming a bottom metal feature of a first metal in a lower portion of the trench by a selective deposition; depositing a barrier layer in an upper portion of the trench, the barrier layer directly contacting both a top surface of the bottom metal feature and sidewalls of the dielectric layer; and forming a top metal feature of a second metal on the barrier layer, filling in the upper portion of the trench, wherein the second metal is different from the first metal in composition.