FinFET Channel Composition for Uniform Threshold Voltage
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Solution Overview
Problem
As semiconductor devices, such as FinFETs, undergo miniaturization, the diffusion of dopants from source/drain regions into the channel region leads to non-uniform threshold voltage, making it difficult to control the ON and OFF states effectively and degrading device performance.
Innovation Solution
The concentration of stress-inducing materials like germanium is varied in the channel region to compensate for the dopant diffusion, achieving a substantially uniform threshold voltage by adjusting the germanium concentration based on the dopant profile, using a gradient layer and buffer layers to optimize carrier mobility and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the minimum feature size is reduced to improve integration density, then more components can be integrated into a given area, but dopant diffusion becomes more significant causing non-uniform threshold voltage
Solution Approach 1:
The patent applies local quality by creating a non-uniform germanium concentration distribution within the channel region. Specifically, the germanium concentration is higher near the source/drain regions and lower toward the center of the channel, allowing different portions of the channel to have different material properties that compensate for dopant diffusion effects locally while maintaining overall device functionality
Solution Approach 2:
The patent changes the compositional parameter of the channel material by varying the germanium concentration as a function of position along the channel. This gradient in germanium content (from approximately 0% to 10% or higher) modifies the physical properties of the channel material to counteract dopant diffusion, thereby maintaining uniform threshold voltage despite miniaturization
2Power
If dopant concentration is increased in source/drain regions to improve device performance, then ON state current increases, but dopant diffusion into the channel region increases causing threshold voltage non-uniformity
Solution Approach 1:
The patent applies preliminary anti-action by pre-configuring the channel material composition (with graded germanium content) before dopant diffusion occurs. This pre-engineered material gradient creates a compensating effect that counteracts the harmful threshold voltage non-uniformity caused by dopant diffusion, allowing high dopant concentrations in source/drain regions to be used without sacrificing threshold voltage uniformity
Solution Approach 2:
The non-uniform germanium distribution creates local variations in channel material properties that specifically address the local dopant diffusion problem near source/drain regions, while maintaining appropriate channel characteristics in the center region for optimal current flow
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 ensures a uniform threshold voltage across the FinFET device, improving its performance and control by counteracting the effects of dopant diffusion, thereby enhancing the device's operational reliability and efficiency.
Implementation Method 1
a concentration of the stress-inducing material in the channel region is varied in accordance with a concentration of the diffused dopant in the channel region to achieve a uniform threshold voltage
Data Source
AI summary
A semiconductor device includes a substrate; a fin protruding above the substrate, the fin including a compound semiconductor material that includes a semiconductor material and a first dopant, the first dopant having a different lattice constant than the semiconductor material, where a concentration of the first dopant in the fin changes along a first direction from an upper surface of the fin toward the substrate; a gate structure over the fin; a channel region in the fin and directly under the gate structure; and source/drain regions on opposing sides of the gate structure, the source/drain regions including a second dopant, where a concentration of the second dopant at a first location within the channel region is higher than that at a second location within the channel region, where the concentration of the first dopant at the first location is lower than that at the second location.