LDBiMOS Composite Device for High Voltage Switching
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Solution Overview
Problem
Conventional high voltage laterally diffused metal oxide semiconductor (LDMOS) devices suffer from low breakdown voltage, high on-resistance, and excess gate charges, limiting their performance in modern electronics applications.
Innovation Solution
A composite semiconductor device is created by integrating an MOS transistor built in a silicon-on-insulator (SOI) layer with a bipolar transistor, where the drain of the MOS transistor serves as the emitter of the bipolar transistor, and the base is coupled to the gate through a resistive element, forming a lateral diffused bipolar MOS (LDBiMOS) device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LDMOS device structure is used, then manufacturing process is simple, but breakdown voltage is low
Solution Approach 1:
The patent combines an LDMOS transistor with a bipolar transistor into a single integrated device structure. The LDMOS provides voltage control while the bipolar transistor enhances breakdown voltage through its inherent voltage-blocking capability, resolving the contradiction between simple structure and high breakdown voltage by merging two device types into one composite structure.
Solution Approach 2:
The device employs a composite structure integrating LDMOS and bipolar transistor regions with different doping profiles and structural characteristics. The LDMOS region (n-type well, p-type body, n-type drain) is combined with the bipolar region (n-type emitter, p-type base, n-type collector) to create a composite semiconductor device that leverages the strengths of both transistor types.
2Reliability
If conventional LDMOS device structure is used, then device structure is simple, but on-resistance is high
Solution Approach 1:
The integration of the bipolar transistor with the LDMOS creates a composite device where the bipolar transistor's low on-resistance characteristic complements the LDMOS structure. The shared drain-emitter region and interconnected terminals reduce the overall on-resistance while maintaining structural efficiency.
3Reliability
If conventional LDMOS device structure is used, then manufacturing is cost-effective, but gate charges are excessive
Solution Approach 1:
The combined LDMOS-bipolar structure allows the gate of the LDMOS to control both the MOS channel and the bipolar transistor base-emitter junction. This merged control mechanism reduces the total gate charge required compared to a conventional LDMOS, as the bipolar transistor's charge storage characteristics are utilized more efficiently.
4Speed
If conventional LDMOS device structure is used, then switching speed is limited by gate charges, but device structure is simpler
Solution Approach 1:
The integrated LDMOS-bipolar structure improves switching speed by combining the fast voltage-controlled characteristics of the LDMOS gate with the rapid switching capability of the bipolar transistor. The shared control node and reduced gate charge result in faster turn-on and turn-off times despite the increased structural complexity.
Data Source
AI summary
A semiconductor device includes a semiconductor-on-insulator region on a substrate. The semiconductor-on-insulator region includes a first semiconductor region overlying a dielectric region. The device includes an MOS transistor and a bipolar transistor. The MOS transistor has a drain region, a body region, and a source region in the first semiconductor region. The MOS transistor also includes a gate. The device also includes a second semiconductor region overlying the substrate and adjacent to the drain region, and a third semiconductor region overlying the substrate and adjacent to the second semiconductor region. The bipolar transistor includes has the drain region of the MOS transistor as an emitter, the second semiconductor region as a base, and the third semiconductor region as a collector. Accordingly, the drain of the MOS transistor also functions as the emitter of the bipolar transistor. Additionally, the gate and the base are coupled by a resistive element.