Metal Nitride Gate Stack Work Function Tuning for MOSFET Scaling
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Solution Overview
Problem
The challenge of scaling down CMOS devices to smaller feature sizes necessitates the replacement of gate oxide and polysilicon gate electrodes with high-k gate dielectric and metal gate electrodes to improve device performance, requiring precise control of the work function of the metal gate.
Innovation Solution
A method involving atomic layer deposition (ALD) with in-situ argon plasma treatment (ALA) is used to adjust the work function of metal gates at low temperatures, enhancing the tunability and physical properties of metal gates in nanoscale MOS devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate oxide and polysilicon gate electrode are replaced with high-k gate dielectric and metal gate electrode, then device performance is improved, but manufacturing precision requirement increases
Solution Approach 1:
The patent applies parameter changes by systematically varying the composition ratio of metal elements (e.g., Ti, Al, Ta) in the metal gate electrode and adjusting the thickness of the high-k gate dielectric layer. By changing these physical and chemical parameters during the deposition process, the work function of the metal gate is precisely controlled to achieve the desired device performance while maintaining manufacturability.
2Productivity
If feature size is scaled down, then production efficiency is increased and cost is lowered, but power dissipation increases
Solution Approach 1:
The patent addresses power dissipation in scaled-down devices by optimizing the work function of the metal gate through parameter changes in material composition. By adjusting the metal element ratios and gate dielectric properties, the device operates at lower voltages, reducing power consumption while maintaining the benefits of scaled geometry for improved production efficiency.
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 approach allows for precise control of the work function, reducing power consumption and improving the electronic performance of MOSFET devices by modulating the physical and material properties of metal gates with atomic-scale accuracy.
Implementation Method 1
in-situ argon plasma treatment (ALA) is used to adjust the work function of metal gates at low temperatures
Implementation Method 2
A method involving atomic layer deposition (ALD) with in-situ argon plasma treatment (ALA) is used to adjust the work function of metal gates
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a gate structure over a channel region of the semiconductor substrate, and n-type doped source/drain features on opposite sides of the channel region. The gate structure includes a gate dielectric layer, a gate metal, and a metal nitride layer between the gate dielectric layer and the gate metal. The metal nitride layer has a work function less than 4.5 eV and a density in a range from 5 g/cm3 to 6 g/cm3.