Titanium Tungsten Gate Stack for Antimonide HEMTs
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Solution Overview
Problem
The selection of a gate structure for high electron mobility transistors (HEMT) with antimonide-based compound semiconductors is challenging due to the thin barrier layer, leading to gate sinking and degradation of transistor characteristics, especially under high processing temperatures.
Innovation Solution
A gate stack comprising a base layer of titanium and tungsten, with a gate barrier layer of titanium and platinum, is formed on an upper barrier layer of indium, aluminum, and arsenic to prevent diffusion and provide thermal stability, while a contact layer of titanium, platinum, and gold is used to enhance adhesion and prevent gate sinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If titanium is used to enhance adhesion, then adhesion is improved, but gate sinking occurs due to reaction with the thin barrier layer
Solution Approach 1:
A nitrogen-containing dielectric layer is introduced as an intermediary between the titanium gate electrode and the thin barrier layer. This intermediate layer prevents direct reaction between titanium and the barrier layer, eliminating gate sinking while maintaining adhesion properties.
Solution Approach 2:
The nitrogen-containing dielectric layer is deposited in advance before forming the titanium gate electrode. This preliminary action creates a protective barrier that prevents subsequent harmful reactions during device fabrication and operation.
2Productivity
If high processing temperatures are used, then manufacturing efficiency is improved, but thermal stress degrades transistor characteristics
Solution Approach 1:
The nitrogen-containing dielectric layer serves as a cushioning layer that absorbs and distributes thermal stress during high-temperature processing. This beforehand cushioning prevents stress concentration at the metal-semiconductor interface, protecting transistor characteristics during high-temperature manufacturing.
3Productivity
If a thin barrier layer is used, then device performance is improved, but diffusion protection becomes insufficient
Solution Approach 1:
The nitrogen-containing dielectric layer acts as a diffusion barrier intermediary between the titanium gate electrode and the thin barrier layer. This intermediate layer prevents unwanted diffusion processes while allowing the thin barrier layer to maintain its performance benefits.
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 improves the performance, uniformity, reliability, and manufacturing yields of HEMTs by achieving peak transconductance, low gate leakage current, and pinch-off current, with reduced mechanical stress and thermal stability.
Implementation Method 1
The base layer provides a thermally stable contact with the upper barrier layer
Implementation Method 2
a gate stack comprises a base layer of titanium and tungsten formed on the upper barrier layer
Implementation Method 3
The gate barrier layer prevents the contact layer from diffusing into the ABCS stack
Implementation Method 4
titanium is desirable because it reacts readily with the semiconductor
Implementation Method 5
temperature cycles during the creation of the HEMT create stress at a metal-semiconductor interface
Data Source
AI summary
An apparatus in one example comprises an antimonide-based compound semiconductor (ABCS) stack, an upper barrier layer formed on the ABCS stack, and a gate stack formed on the upper barrier layer. The upper barrier layer comprises indium, aluminum, and arsenic. The gate stack comprises a base layer of titanium and tungsten formed on the upper barrier layer.