Metal Gate Stack With Nitrogen Gradient for RMG Yield
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Solution Overview
Problem
Conventional poly-silicon gates in semiconductor devices face performance issues due to boron penetration and depletion effects, leading to reduced gate capacitance and driving force, necessitating the use of work function metals in metal gate stack structures, where the quality and yield of the semiconductor device are influenced by the replacement metal gate (RMG) process.
Innovation Solution
A semiconductor device with a gate structure comprising a titanium nitride barrier layer, a titanium aluminide layer, and a middle layer containing titanium and nitrogen, where the nitrogen concentration decreases vertically towards the interface with the titanium aluminide layer, and a manufacturing method involving the formation of these layers to enhance the RMG process and improve device yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional poly-silicon is used as gate electrode, then manufacturing process is simple, but performance deteriorates due to boron penetration and depletion effects
Solution Approach 1:
The patent employs a composite gate electrode structure consisting of multiple layers including titanium nitride barrier layer, titanium aluminide layer, and middle layer with specific nitrogen concentration gradient. This composite structure replaces conventional poly-silicon to eliminate boron penetration and depletion effects while maintaining manufacturing feasibility through established PVD/CVD processes.
Solution Approach 2:
The middle layer is designed with a nitrogen concentration gradient where nitrogen concentration is gradually decreased in the vertical direction towards the interface with the titanium aluminide layer. This local variation in composition optimizes both barrier properties and electrical performance at different depths of the gate structure.
2Reliability
If work function metals are used to replace poly-silicon gate, then gate capacitance and driving force are improved, but manufacturing complexity increases
Solution Approach 1:
The gate electrode is segmented into multiple functional layers: titanium nitride barrier layer, titanium aluminide layer, and middle layer with nitrogen concentration gradient. Each layer performs a specific function (barrier, work function adjustment, transition), allowing optimization of gate performance while managing complexity through modular design.
Solution Approach 2:
The nitrogen concentration in the middle layer is varied as a gradient parameter, decreasing vertically towards the titanium aluminide interface. This parameter change enables continuous optimization of electrical properties and interface characteristics without requiring discrete additional layers.
3Reliability
If replacement metal gate process is used, then device performance is enhanced, but manufacturing yield becomes more sensitive to process variations
Solution Approach 1:
The titanium nitride barrier layer is formed first to prevent boron penetration and establish a stable foundation before subsequent layers are deposited. This preliminary barrier layer ensures that even if process variations occur in later steps, the fundamental gate performance and reliability are protected.
Solution Approach 2:
The middle layer with nitrogen concentration gradient acts as an intermediary between the titanium nitride barrier layer and the titanium aluminide layer. It provides a transition zone that manages interface properties and reduces sensitivity to process variations, ensuring stable metal gate quality.
Data Source
AI summary
A semiconductor device includes a substrate and a gate structure. The gate structure is disposed on the substrate, and the gate structure includes a titanium nitride barrier layer a titanium aluminide layer, and a middle layer. The titanium aluminide layer is disposed on the titanium nitride barrier layer, and the middle layer is disposed between the titanium aluminide layer and the titanium nitride barrier layer. The middle layer is directly connected with the titanium aluminide layer and the titanium nitride barrier layer, and the middle layer includes titanium and nitrogen. A concentration of nitrogen in the middle layer is gradually decreased in a vertical direction towards an interface between the middle layer and the titanium aluminide layer.