Gate-All-Around Nanosheet Sagging via Strained SiGe Buffer
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Solution Overview
Problem
Gate-all-around transistors with long channels experience sagging due to surface tension, which reduces effective channel area and degrades gate control, posing a challenge for optimizing device behavior in I/O devices.
Innovation Solution
A strained relaxed silicon germanium alloy buffer layer is employed to induce tensile strain in semiconductor channel material nanosheets, keeping them straight and reducing sagging, with a method involving a semiconductor material stack structure and sacrificial gate structures to form suspended nanosheets wrapped by a functional gate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate-all-around transistors with long channels are used, then gate control is improved, but sagging occurs due to surface tension reducing effective channel area
Solution Approach 1:
The patent applies tensile strain to the semiconductor channel material nanosheets through a strained relaxed silicon germanium alloy buffer layer. This parameter change in the material's physical state (inducing tensile strain) counteracts the surface tension forces causing sagging, thereby maintaining the nanosheets in a straight configuration and preserving the effective channel area while retaining long channel gate control benefits
2Reliability
If suspended nanosheets are formed for gate-all-around structure, then electrostatic control is improved, but sagging is caused by surface tension
Solution Approach 1:
The patent changes the physical parameter of the nanosheet by inducing tensile strain through the strained relaxed silicon germanium alloy buffer layer. This strain modification alters the mechanical properties of the nanosheet, making it resistant to surface tension-induced sagging and maintaining its straight shape, thereby preserving both electrostatic control and structural integrity
Solution Approach 2:
The strained relaxed silicon germanium alloy buffer layer acts as an intermediary between the substrate and the semiconductor channel material nanosheets. This buffer layer transfers tensile strain to the nanosheets, serving as a mediator that counteracts surface tension forces and maintains nanosheet straightness without directly interfering with the gate-all-around structure's electrostatic control
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
The solution effectively reduces and eliminates sagging, maintaining the integrity of the channel area and improving gate control, thereby enhancing the performance of long channel device behavior.
Implementation Method 1
A strained relaxed silicon germanium alloy buffer layer is employed to induce a tensile stain on each suspended semiconductor channel material nanosheet
Implementation Method 2
Nanosheet formation relies on the selective removal of one semiconductor material relative to another semiconductor material to form suspended nanosheets
Data Source
AI summary
A strained relaxed silicon germanium alloy buffer layer is employed in the present application to induce a tensile stain on each suspended semiconductor channel material nanosheet within a nanosheet material stack that is present in a long channel device region of a semiconductor substrate. The induced tensile strain keeps the suspended semiconductor channel material nanosheets that are present in long channel device region essentially straight in a lateral direction. Hence, reducing and even eliminating the sagging effect that can be caused by surface tension.