MOS Transistor Gate Structure with High-k Dielectric and Metal Electrode
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Solution Overview
Problem
The decreasing gate length and channel length in MOS transistors pose challenges in increasing capacitance and enhancing operating characteristics, as silicon oxide films reach physical limits in electric properties, and polysilicon gate electrodes have high resistance, necessitating the use of high-k dielectric films and metal gate electrodes.
Innovation Solution
A semiconductor device with specific trench structures, liner patterns, work function metals, barrier metals, and fill metals is designed, including high-k dielectric films and rare earth metal films, to optimize the gate structure and reduce leakage current, with varying thicknesses and volumes of metals to adjust threshold voltage accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon oxide film is used as gate insulating film, then manufacturing process is simple and compatibility is good, but electric properties reach physical limit when thickness decreases
Solution Approach 1:
The patent uses a composite gate insulating film structure combining silicon oxide film and high-k dielectric film. The silicon oxide film provides good interface properties and manufacturing compatibility, while the high-k dielectric film layer provides high dielectric constant to maintain capacitance at reduced thickness, thus resolving the contradiction between electric properties and manufacturing ease.
2Reliability
If polysilicon is used as gate material, then manufacturing process is established, but resistance is greater than metals
Solution Approach 1:
The patent changes the material parameter from polysilicon to metal for the gate electrode, thereby reducing resistance. The metal gate electrode maintains compatibility with existing manufacturing processes while achieving lower resistance compared to polysilicon, resolving the contradiction between reliability and ease of manufacture.
3Reliability
If high-k dielectric film replaces silicon oxide film, then leakage current is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent employs a composite gate insulating film structure where silicon oxide film and high-k dielectric film are combined. This allows the high-k dielectric film to reduce leakage current while the silicon oxide film maintains good interface properties and manufacturing compatibility, thus reducing the perceived manufacturing complexity.
4Length of moving object
If gate length and channel length are decreased, then feature size is reduced, but capacitance between gate and channel decreases
Solution Approach 1:
The patent changes the dielectric constant parameter by introducing high-k dielectric film into the gate insulating film structure. This increases the capacitance between gate and channel despite the reduced gate length and channel length, as the high-k material compensates for the reduced physical dimensions through its higher dielectric constant.
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 configuration enhances the operating characteristics of MOS transistors by reducing leakage current, increasing capacitance, and allowing precise adjustment of threshold voltage, thereby improving transistor performance.
Implementation Method 1
a high-k dielectric film having high dielectric constant may replace the silicon oxide film. The high-k dielectric film may reduce leakage current between gate electrode and channel region
Implementation Method 2
a rare earth metal film between the liner pattern and the high-k dielectric film
Data Source
AI summary
A semiconductor device includes a first trench and a second trench, a liner pattern along a portion of side surfaces and along bottom surfaces of the first and the second trenches, respectively, a work function metal in the first and the second trenches and on the liner pattern, respectively, a first barrier metal in the first trench and on the work function metal, and having a first thickness, a second barrier metal in the second trench and on the work function metal, and having a second thickness thicker than the first thickness, and a first fill metal on the first barrier metal.