High-k Metal Gate Transistor with Reaction Prevention Layer
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Solution Overview
Problem
Thinner silicon oxide gate insulating layers in MOS transistors lead to increased leakage currents and reduced device reliability, necessitating the use of high dielectric constant materials and metal gate electrodes to maintain performance, but these solutions do not fully address the reliability issues.
Innovation Solution
A semiconductor device design featuring a substrate with distinct regions, where the first region has a high-voltage gate insulating layer and a reaction prevention layer on the bottom surface of trenches, and the second region has a high-k insulating layer with a capping layer on the sidewalls and bottom, along with replacement metal gate structures that directly contact the reaction prevention layer, optimizing the gate insulating layers and metal gate structures for improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the thickness of silicon oxide gate insulating layer is reduced, then gate capacitance is improved, but leakage current increases dramatically
Solution Approach 1:
The patent changes the dielectric constant parameter of the gate insulating layer material from silicon oxide (k≈3.9) to high-k materials (k>7), enabling thinner effective gate insulator thickness for achieving required gate capacitance while maintaining lower leakage currents due to the higher barrier properties of high-k materials
Solution Approach 2:
The patent employs composite gate structures combining high-k insulating layers with metal gate electrodes and reaction prevention layers, creating a multi-layer composite system that simultaneously achieves high gate capacitance and low leakage current by leveraging the complementary properties of each material layer
2Reliability
If high-k insulating layers are used to reduce leakage current, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent segments the gate structure into distinct functional layers: high-k insulating layer for dielectric function, reaction prevention layer for interface protection, and metal gate layer for electrode function, allowing each layer to be optimized independently while simplifying the overall fabrication process through standardized layer-by-layer deposition
3Power
If metal gate electrodes replace polysilicon gates, then performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent forms the reaction prevention layer on the high-k insulating layer before depositing the metal gate electrode, preventing harmful reactions between the metal and insulator during subsequent thermal processing steps, thereby simplifying the overall fabrication process by eliminating the need for complex in-situ oxidation or annealing procedures that would otherwise be required
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
This design effectively reduces leakage currents and enhances the reliability of MOS transistors by using high-k insulating layers and metal gate structures, maintaining performance while improving device reliability and power efficiency.
Implementation Method 1
High dielectric constant materials (also referred to as high-k materials) have been substituted for silicon oxide in the gate insulating layer, allowing increased gate capacitance (and increased performance) without suffering the consequences of the relatively high leakage currents associated with thin silicon dioxide layers
Implementation Method 2
a reaction prevention layer which is formed on the first gate insulating layer on the bottom surface of the first trench
Data Source
AI summary
A semiconductor device includes an interlayer insulating film formed on a substrate, the insulating layer including a trench. A gate insulating layer is formed on a bottom surface of the trench and a reaction prevention layer is formed on the gate insulating layer on the bottom surface of the trench. A replacement metal gate structure is formed on the reaction prevention layer of the trench to fill the trench.