MOSFET-BJT Switching Structure for High Current CMOS Integration
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Solution Overview
Problem
Conventional semiconductor devices, such as MOSFETs and BJTs, face challenges in achieving high current capability and fast switching speed while being compatible with low-cost CMOS processes, limiting their use in VLSI applications.
Innovation Solution
A hybrid device combining a MOSFET and a BJT, where the MOSFET's body region acts as the BJT's base, allowing for high current conduction by impact-ionization generated holes, and is fabricated using bulk CMOS processes, enabling easy scaling down to sub-50 nm dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If MOSFET is used for high current conduction, then current capability is improved, but switching speed deteriorates
Solution Approach 1:
The patent combines MOSFET and BJT into a single integrated device structure where the MOSFET body region serves as the BJT base region. This merging allows the device to leverage the high input impedance and fast switching of MOSFET while utilizing the high current conduction capability of BJT, thereby resolving the contradiction between current capability and switching speed.
Solution Approach 2:
The combined device performs multiple functions within a single structure: the MOSFET component provides fast switching and voltage control, while the BJT component provides high current conduction. The shared body/base region enables both transistor types to operate simultaneously, achieving multi-functionality that resolves the performance trade-off.
2Power
If BJT-based devices (LDMOS, VDMOS, V-groove) are used for high current conduction, then current capability is improved, but fabrication complexity increases
Solution Approach 1:
The patent merges the BJT high-current advantage with MOSFET fabrication simplicity by integrating both transistor functions into a single device that can be manufactured using standard CMOS processes. This eliminates the need for complex BJT-specific fabrication steps while retaining high current capability through the BJT action in the combined structure.
3Area of moving object
If device size is reduced for VLSI integration, then integration density is improved, but current capability deteriorates
Solution Approach 1:
The combined MOSFET-BJT structure achieves high current capability in a compact footprint by utilizing the vertical current conduction path of the BJT component. The integrated structure allows high current to flow through a small area, enabling VLSI integration while maintaining high power handling capability that would otherwise require larger device dimensions.
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 hybrid device achieves high power handling and simple fabrication, facilitating its use in VLSI applications by delivering high current efficiently and being compatible with CMOS processes, thus overcoming the limitations of conventional devices.
Implementation Method 1
the resulting field effect channel allows the electrons to flow from one node (e.g., the source) to another node (e.g., the drain). The movement of the electrons causes a large number of holes to be generated in the body through a mechanism called impact-ionization.
Data Source
AI summary
A switching device and methods of making and operating the same are provided. In one aspect, a method of operating a switching device is provided that includes providing a MOS transistor that has a gate, a source region, a drain region and a body region. A bipolar transistor is provided that has a collector, a base and an emitter. The body region of the MOS transistor serves as the base of the bipolar transistor and the drain region of the MOS transistor serves as the collector of the bipolar transistor. Activation of the MOS transistor causes the bipolar transistor to turn on. The MOS transistor is activated to turn on the bipolar transistor and the bipolar transistor delivers current to the source region.