SOI MOSFET Conducting Structure for Floating Body Suppression
Solution Overview
Problem
Metal oxide semiconductor field effect transistors (MOSFETs) built on silicon-on-insulator (SOI) substrates face challenges with floating body effect, leading to varying threshold voltages and dynamic sub-threshold voltage leakage due to body charge storage, which complicates control and prediction of device performance.
Innovation Solution
A semiconductor structure comprising a first insulation layer, a first semiconductor layer with transistors, and a conducting structure under the channel region, which is either within or in contact with the semiconductor layer, helps to mitigate the floating body effect by providing a path for carrier removal through the conducting structure, which is typically made of metal and heavily doped, and is spaced apart from or in contact with the source and drain regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conducting structure is placed under the channel region to reduce floating body effect, then threshold voltage stability is improved, but device structure complexity increases
Solution Approach 1:
The conducting structure is nested within the semiconductor layer itself, utilizing the existing layer structure. The conducting structure is formed as a region within the semiconductor layer that extends from the first interface to the second interface, effectively nesting the solution within the existing device architecture rather than adding external components.
Solution Approach 2:
The conducting structure is positioned in the vertical dimension under the channel region, extending through the semiconductor layer thickness. This vertical placement creates a new spatial dimension for charge removal that does not interfere with the lateral device layout, allowing threshold voltage control without increasing planar device complexity.
2Productivity
If the conducting structure is made of metal, then carrier removal efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The conducting structure serves multiple functions: it acts as a charge removal path to reduce floating body effect, provides threshold voltage control, and can serve as a diffusion barrier. By combining multiple functions into a single structure, the patent avoids the need for separate metal layers and additional processing steps that would increase manufacturing complexity.
Solution Approach 2:
The patent allows flexibility in the conducting structure material composition, permitting metals, heavily doped semiconductor regions, or other conductive materials. This parameter change enables selection based on existing manufacturing capabilities and process compatibility, reducing the need for new fabrication techniques while maintaining effective carrier removal.
3Reliability
If the conducting structure is heavily doped, then electrical conductivity is improved, but doping precision control becomes more difficult
Solution Approach 1:
The conducting structure is formed during the semiconductor layer formation process itself, before final device fabrication steps. By establishing the conducting region early in the process when the semiconductor layer is being created, the doping is performed under controlled conditions with precise temperature and time parameters, ensuring consistent heavy doping without requiring subsequent complex doping steps.
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 proposed solution effectively reduces the floating body effect, stabilizing threshold voltages and minimizing leakage, thereby enhancing the reliability and performance of SOI MOSFETs by allowing for better control over carrier accumulation in the channel region.
Implementation Method 1
The conducting structure is disposed under the first channel region and spaced apart from the first drain region. The conducting structure is disposed over the first insulation layer and either within or in contact with the first semiconductor layer.
Data Source
AI summary
The present disclosure relates to semiconductor structures and methods for making the same. The semiconductor structure comprises a first insulation layer, a first semiconductor layer, and a conducting structure. The first semiconductor layer is over the first insulation layer. The first semiconductor layer comprises a first transistor. The first transistor comprises a first source region, a first drain region, and a first channel region under a first gate disposed over the first semiconductor layer. The conducting structure is disposed under the first channel region and spaced apart from the first drain region. The conducting structure is disposed over the first insulation layer and either within or in contact with the first semiconductor layer.