FinFET Epitaxy Below STI for Short-Channel and Fin-Bending Control
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Solution Overview
Problem
In the formation of Fin Field-Effect Transistors (FinFETs), the existing methods face challenges in controlling the epitaxy regions to prevent merging and ensure proper extension below Shallow Trench Isolation (STI) regions, leading to issues like short channel effects and fin bending.
Innovation Solution
The method involves forming semiconductor fins with recesses extending below the top surfaces of STI regions, followed by growing epitaxy regions that extend to these recesses, using a multi-layer epitaxy process with controlled doping concentrations and stressor layers to optimize the source/drain regions, and forming p-type FinFETs with cone-shaped epitaxy regions to mitigate fin bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If epitaxy regions are grown from recesses of neighboring semiconductor fins, then source/drain regions are formed, but the epitaxy regions may merge with each other causing planar top surfaces and potential short channel effects
Solution Approach 1:
The patent applies preliminary action by forming a shielding layer pattern before epitaxy growth. This shielding layer is deposited and patterned to extend beyond the STI regions, creating a pre-configured structure that guides and confines the subsequent epitaxy region growth. The shielding layer prevents unwanted merging of epitaxy regions from neighboring fins while ensuring proper extension below STI regions, thereby resolving the contradiction between manufacturing precision and device reliability.
2Reliability
If epitaxy regions extend below STI regions, then short channel effect is reduced, but control over epitaxy region profile and merging becomes difficult
Solution Approach 1:
The patent implements feedback control through the shielding layer mechanism. The shielding layer is strategically positioned and dimensioned to provide real-time confinement during epitaxy growth. As epitaxy regions grow from recesses of neighboring fins, the shielding layer acts as a physical barrier that prevents merging while allowing extension below STI regions. This feedback mechanism ensures that the epitaxy regions maintain the desired profile and extension depth, resolving the contradiction between reliability improvement and manufacturing precision.
3Manufacturing precision
If multi-layer epitaxy process with doping is used, then dopant control is enhanced, but process complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the epitaxy process into multiple distinct layers with different doping concentrations and materials. The multi-layer epitaxy structure includes separately formed layers, each with specific dopant profiles, allowing precise control over dopant distribution in the source/drain regions. This segmentation approach enhances manufacturing precision for dopant control while organizing the complexity into manageable, functionally distinct layers.
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 effectively reduces the short channel effect, enhances dopant control, and improves fin stability by extending epitaxy regions below STI levels, thereby enhancing the performance and reliability of FinFETs.
Implementation Method 1
growing epitaxy regions that extend to these recesses, using a multi-layer epitaxy process
Data Source
AI summary
A method includes forming isolation regions extending into a semiconductor substrate, forming a plurality of semiconductor fins protruding higher than top surfaces of the isolation regions, forming a gate stack on the plurality of semiconductor fins, forming a gate spacer on a sidewall of the gate stack, and recessing the plurality of semiconductor fins to form a plurality of recesses on a side of the gate stack. The plurality of recesses extend to a level lower than top surfaces of the isolation regions. Epitaxy processes are performed to grow an epitaxy region, wherein the epitaxy region fills the plurality of recesses.