MOSFET-BJT Switching Structure for High-Current CMOS Integration
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Solution Overview
Problem
Conventional semiconductor devices struggle to combine high current capability with simple fabrication and compatibility with low-cost CMOS processes, limiting their use in VLSI applications.
Innovation Solution
A device integrating a MOSFET and a BJT, where the MOSFET's body region serves as the BJT's base, enabling high current conduction by impact-ionization-induced hole generation, and fabricated using bulk CMOS processes for scalability and ease of production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a MOSFET is used for high current conduction, then the device structure is simple and fabrication is easy, but the current capability is insufficient
Solution Approach 1:
The patent combines a MOSFET and a BJT into a single integrated device structure. The MOSFET provides easy fabrication and control, while the BJT provides high current capability. The body region of the MOSFET serves as the base of the BJT, creating a unified device that leverages the strengths of both transistor types to resolve the contradiction between ease of manufacture and current capability.
Solution Approach 2:
The device structure serves multiple functions: the MOSFET portion provides voltage-controlled switching and ease of fabrication, while the BJT portion provides high current conduction. This multi-functional design allows a single device to fulfill both the manufacturing simplicity requirement and the high current capability requirement that were in contradiction.
2Reliability
If a BJT is used for high current capability, then the current conduction is excellent, but the fabrication process becomes complex and incompatible with CMOS
Solution Approach 1:
By merging the MOSFET and BJT structures, the patent enables the BJT to be fabricated using standard CMOS processes. The shared body region and integrated structure allow the BJT to be created as part of the conventional CMOS fabrication sequence, eliminating the need for separate complex BJT fabrication processes while maintaining high current capability.
3Ease of manufacture
If conventional MOSFET structure is used, then fabrication is simple, but power handling capability is limited
Solution Approach 1:
The integrated MOSFET-BJT structure allows the device to handle high power by combining the voltage control advantage of the MOSFET with the high current capability of the BJT. The MOSFET's gate controls the base current of the BJT, which then provides high current conduction, enabling high power handling while maintaining fabrication simplicity.
4Productivity
If device size is scaled down for VLSI, then integration density increases, but current capability decreases
Solution Approach 1:
The compact integrated structure allows the MOSFET and BJT to share common regions (body, substrate), reducing the overall device footprint. This enables high integration density for VLSI applications while the BJT component maintains high current capability despite the reduced size, resolving the contradiction between scaling and current performance.
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 integrated device achieves high power handling and simple fabrication, allowing for efficient current delivery and scalability to sub-50 nm dimensions, addressing the limitations of existing devices in VLSI applications.
Implementation Method 1
The MOSFET is typically turned on by applying a voltage to a gate to create a field effect channel
Implementation Method 2
The movement of the electrons causes a large number of holes to be generated in the body through a mechanism called impact-ionization
Implementation Method 3
a BJT typically is turned on by forward biasing a PN junction which renders the device conductive
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.