Refractory Metal Barrier Gate Structure for Semiconductor Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor devices, metal gate structures face issues such as gate sinking and metal-semiconductor inter-reaction, leading to performance degradation due to diffusion of gate metals into the semiconductor substrate during high-temperature processing.
Innovation Solution
A transistor device with a gate structure comprising a layer of tantalum nitride (TaNx), a layer of titanium (Ti), and a layer of gold (Au), where the TaNx layer acts as a diffusion barrier to prevent gate sinking, and additional layers of TaNx and Ti are used to inhibit diffusion of the Au layer into the compound semiconductor substrate, formed using electron-beam evaporation to ensure stability and prevent inter-reaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a metal gate structure is used to enable higher clock speeds and lower power consumption, then device performance is improved, but gate sinking and metal-semiconductor inter-reaction occur leading to performance degradation
Solution Approach 1:
The gate structure is segmented into multiple functional layers: a Schottky barrier metal layer (Au, Ag, or Al) for electrical performance, a refractory metal barrier layer (TaNx, TiN, or WSix) for diffusion prevention, and an adhesion layer (Ti, Pt, or Pd) for structural stability. This segmentation allows each layer to perform its specific function, preventing gate sinking while maintaining the electrical benefits of metal gates.
Solution Approach 2:
The refractory metal barrier layer acts as an intermediary between the Schottky barrier metal and the compound semiconductor substrate. This intermediate layer prevents direct contact and inter-reaction between the metal gate and semiconductor, blocking diffusion pathways while allowing the Schottky barrier properties to be maintained.
2Reliability
If gate metal is used to provide Schottky barrier properties, then electrical performance is improved, but diffusion into the semiconductor substrate occurs during high-temperature processing
Solution Approach 1:
The refractory metal barrier layer serves as a mediator that blocks the diffusion pathway between the Schottky barrier metal and the semiconductor substrate. Materials like TaNx, TiN, and WSix are chosen for their high thermal stability and low diffusivity, creating an effective diffusion barrier during high-temperature processing while allowing the Schottky barrier metal to maintain its electrical properties.
Solution Approach 2:
The gate structure uses a composite material system combining Schottky barrier metals (Au, Ag, Al) with refractory metal nitrides or silicides (TaNx, TiN, WSix). This composite structure leverages the electrical properties of the Schottky metal and the barrier properties of the refractory material, creating a multi-functional gate structure that prevents metal loss while maintaining electrical performance.
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 solution effectively prevents gate sinking and metal-semiconductor inter-reaction, maintaining device performance and reliability by forming a stable refractory metal barrier that limits diffusion and maintains Schottky barrier properties, even at elevated temperatures.
Implementation Method 1
an electron-beam evaporated gate structure including a layer of tantalum nitride (TaNx), a layer of titanium (Ti) and a layer of gold (Au)
Implementation Method 2
The layer of TaNx may be configured to provide a diffusion barrier between the layer of Au and the compound semiconductor substrate
Data Source
AI summary
Gate structures for semiconductor devices include a silicon nitride layer, an electron beam evaporated tantalum nitride layer disposed on the silicon nitride layer, a first electron beam evaporated titanium layer disposed on the tantalum nitride layer, an electron beam evaporated gold layer deposited on the first titanium layer, and a second electron beam evaporated titanium layer deposited on the gold layer.