Nanowire MOSFET Etch Stop Support Structures
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Solution Overview
Problem
Conventional nanowire-based FET device fabrication techniques face challenges with etch undercutting beneath the source and drain regions due to isotropic etching, which compromises structural support and leads to undesirable diffusion of materials during high-temperature processes.
Innovation Solution
Incorporating etch stop layers, such as carbon-doped silicon or boron-doped silicon, beneath the source and drain regions to act as support structures and prevent the etching of sacrificial materials, ensuring selective etching and maintaining structural integrity of the nanowire channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If isotropic etching is used to remove sacrificial material beneath the nanowire channel, then the nanowire channel can be suspended, but etch undercutting occurs beneath the source and drain regions compromising structural support
Solution Approach 1:
The patent segments the sacrificial material removal process by introducing etch stop layers that divide the etching domain. These layers create distinct zones: one where etching proceeds to suspend the nanowire channel, and another where etching is halted to preserve structural support beneath the source and drain regions. This segmentation resolves the contradiction by allowing selective suspension without compromising structural integrity.
Solution Approach 2:
The etch stop layers introduce local quality variations in the sacrificial material structure. By doping specific regions with carbon or boron, the patent creates areas with different etch resistances. The regions beneath the source and drain maintain higher structural strength due to enhanced etch resistance, while other regions allow etching for channel suspension. This local differentiation resolves the contradiction between suspension and structural support.
2Loss of substance
If etching proceeds beneath source and drain regions, then complete sacrificial material removal is achieved, but material diffusion occurs during high-temperature processes
Solution Approach 1:
The patent applies preliminary action by forming etch stop layers before the sacrificial material removal process. These pre-formed layers with enhanced etch resistance prevent unwanted etching and subsequent material diffusion during high-temperature processing. By establishing protective barriers in advance, the patent eliminates the harmful diffusion effect while maintaining complete sacrificial material removal in appropriate regions.
Solution Approach 2:
The etch stop layers act as intermediary structures between the sacrificial material and the source/drain regions. These intermediate layers with modified composition (carbon-doped or boron-doped silicon) serve as protective mediators that prevent direct interaction between the etching process and the source/drain regions, thereby preventing material diffusion during high-temperature processes while allowing complete removal of sacrificial material where needed.
3Strength
If etch stop layers are introduced to prevent undercutting, then structural integrity is maintained, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the compositional parameters of the sacrificial material through doping with carbon or boron. Instead of introducing entirely new materials or complex multi-layer structures, the patent changes the chemical composition parameters of existing silicon-based sacrificial material to achieve differential etch resistance. This approach maintains structural integrity while minimizing fabrication complexity by using parameter modification rather than structural complexity.
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 use of etch stop layers effectively prevents etch undercutting and material diffusion, enabling the reliable suspension of nanowire channels and maintaining structural and electrical isolation, thus enhancing the fabrication process of nanowire FET devices.
Implementation Method 1
The etching is selective to the sacrificial material to prevent the removal of the etch stop layers beneath the source region and the drain region
Implementation Method 2
Incorporating etch stop layers, such as carbon-doped silicon or boron-doped silicon, beneath the source and drain regions to act as support structures and prevent the etching of sacrificial materials
Data Source
AI summary
A nanowire field effect transistor (FET) device and method for forming the same is disclosed. The device comprises: a semiconductor substrate; a device layer including a source region and a drain region connected by a suspended nanowire channel; and etch stop layers respectively arranged beneath the source region and the drain region, the etch stop layers forming support structures interposed between the semiconductor substrate and the source and drain regions. The suspended nanowire channel is formed by etching a sacrificial material disposed beneath the suspended nanowire channel and between the etch stop layers. The etching is selective to the sacrificial material to prevent the removal of the etch stop layers beneath the source region and the drain region.