NMOS Work Function Adjustment via Selective Oxidation
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Solution Overview
Problem
In semiconductor devices, the reduction in size leads to challenges in filling trenches with metal material due to the need for multiple work function adjustment layers, resulting in poor filling effects and device performance degradation, especially for high threshold voltage NMOS devices with narrow trenches.
Innovation Solution
A method involving oxidation treatments with varying oxygen content on the NMOS work function adjustment layers in different trenches to form oxide layers, allowing for the elimination of multiple PMOS work function adjustment layers and improved trench filling by adjusting the oxygen content in the oxide layers, thereby enhancing the filling effect and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple work function adjustment layers with different thicknesses are formed to achieve multiple threshold voltages, then the threshold voltage requirements are satisfied, but the trench filling becomes difficult and the filling effect deteriorates
Solution Approach 1:
The patent applies local quality by forming different thicknesses of the same work function adjustment layer material in different trenches through selective masking and etching. Each trench receives a locally optimized layer thickness corresponding to its specific threshold voltage requirement, eliminating the need for multiple different materials while maintaining precise control over device characteristics.
Solution Approach 2:
The patent changes the thickness parameter of the work function adjustment layer to achieve different threshold voltages. By controlling the etching depth or deposition thickness in different regions, the same material layer provides different work functions, thereby satisfying multiple threshold voltage requirements without compromising trench filling.
2Adaptability or versatility
If a relatively thick work function adjustment layer is formed in narrow trenches for high threshold voltage devices, then the desired threshold voltage is achieved, but the metal material deposition becomes difficult and the filling effect is poor
Solution Approach 1:
The patent performs preliminary action by pre-forming the work function adjustment layer with the exact required thickness before metal gate deposition. This preliminary thickness optimization ensures that subsequent metal filling can proceed smoothly without void formation, as the trench geometry is already optimized for the upcoming deposition process.
Solution Approach 2:
The patent introduces dynamic control in the work function adjustment layer formation process, allowing the layer thickness to be adjusted according to the specific requirements of each trench. This dynamic approach enables optimization of both the electrical characteristics and the geometric parameters for subsequent metal filling in different device regions.
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 enables better trench filling and device performance by eliminating the need for multiple PMOS work function adjustment layers, improving the air gap for metal electrode layer deposition and stabilizing device performance across different threshold voltages.
Implementation Method 1
performing a first oxidation treatment on the NMOS work function adjustment layer in the first trench to form a first oxide layer; and performing a second oxidation treatment on the NMOS work function adjustment layer in the second trench to form a second oxide layer
Data Source
AI summary
A method of manufacturing a semiconductor device includes providing a substrate structure including a semiconductor substrate, an interlayer dielectric layer on the semiconductor substrate, multiple trenches extending through the interlayer dielectric layer to the semiconductor substrate and including a first trench of a first NMOS device and a second trench of a second NMOS device, and a dielectric layer on sidewalls and a bottom of the trenches, forming an NMOS work function adjustment layer on the dielectric layer, performing a first oxidation treatment on the NMOS work function adjustment layer in the first trench to form a first oxide layer, and a second oxidation treatment on the NMOS work function adjustment layer in the second trench to form a second oxide layer, and forming a metal electrode layer in the trenches. The first oxide layer has an oxygen content lower than that of the second oxide layer.