Semiconductor Metal Gate with Nitrogen-Rich Barrier for TDDB Reduction
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Solution Overview
Problem
Current semiconductor devices, particularly FinFET architecture, face issues with time-dependent dielectric breakdown (TDDB) due to excessive electrical fields, which affects the reliability and performance of metal gate transistors.
Innovation Solution
A semiconductor device structure is developed with a gate structure comprising a high-k dielectric layer and a bottom barrier metal (BBM) layer, which includes a nitrogen-rich top portion and titanium-rich middle and bottom portions, to enhance the electrical properties and reduce TDDB. The BBM layer is deposited in a U-shaped or I-shaped configuration depending on the process approach, with specific materials like TiN and TaN used for the BBM layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional polysilicon gate is used, then fabrication is simplified, but performance deteriorates due to boron penetration and depletion effect
Solution Approach 1:
The patent changes the material parameter of the gate electrode from polysilicon to metal (such as tungsten, titanium nitride, or tantalum nitride), fundamentally altering the electrical and chemical properties to eliminate boron penetration and depletion effects while maintaining fabrication feasibility through modified processes
Solution Approach 2:
The patent employs composite gate structures combining metal layers with dielectric materials (such as high-k dielectrics like hafnium oxide or silicon oxide), creating a composite gate electrode that leverages the advantages of both materials to achieve superior electrical performance and control
2Power
If electrical field is increased to improve device performance, then driving force is enhanced, but time-dependent dielectric breakdown occurs
Solution Approach 1:
The patent uses composite gate structures with metal electrodes and high-k dielectric layers that enable better electrical field distribution and control, allowing enhanced driving force without proportional increase in dielectric stress, thereby reducing TDDB risk
Solution Approach 2:
The patent changes the dielectric material parameters by using high-k materials with higher breakdown field strength, allowing the device to sustain higher electrical fields for improved driving force while maintaining dielectric integrity and reducing TDDB
3Reliability
If gate dielectric layer thickness is increased to reduce electrical field, then TDDB is reduced, but gate capacitance decreases
Solution Approach 1:
The patent changes the dielectric constant parameter by adopting high-k materials (such as hafnium oxide with k>20, or silicon oxide with k=3.9), which enable maintaining thin physical thickness for high capacitance while achieving effective thickness equivalent to thicker low-k layers for TDDB resistance
Solution Approach 2:
The patent creates composite gate dielectric structures combining high-k dielectric layers with interface dielectric layers (such as silicon oxide), optimizing the balance between capacitance and breakdown resistance through layered composite architecture
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 effectively addresses the TDDB issue by improving the electrical properties and reducing the equivalent thickness of the gate dielectric layer, thereby enhancing the driving force and reliability of the semiconductor devices.
Implementation Method 1
the middle portion being a nitrogen rich portion... effectively addresses the TDDB issue by improving the electrical properties and reducing the equivalent thickness of the gate dielectric layer
Implementation Method 2
a gate structure includes a high-k dielectric layer on the substrate... enhancing the electrical properties and reducing the equivalent thickness of the gate dielectric layer
Data Source
AI summary
A semiconductor device includes a substrate and a gate structure on the substrate, in which the gate structure includes a high-k dielectric layer on the substrate and a bottom barrier metal (BBM) layer on the high-k dielectric layer. Preferably, the BBM layer includes a top portion, a middle portion, and a bottom portion, the middle portion being a nitrogen rich portion, the top portion and the bottom portion being titanium rich portions, and the top portion, the middle portion, and the bottom portion are of same material composition.