High-Voltage MOSFET Body Isolation to Suppress Body Effect
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Solution Overview
Problem
Traditional high-voltage semiconductor devices, such as LDMOSFETs, suffer from body effect issues that reduce the driving current and performance as the voltage applied to the source region increases.
Innovation Solution
A high-voltage semiconductor device is designed with a doping region having a conductivity type different from that of the body region, which isolates the body region from the substrate, thereby reducing or eliminating the body effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the source region is electrically connected to the underlying p-type semiconductor substrate via the body region, then the device structure is simple and manufacturing is easy, but the body effect is induced which reduces the driving current and transistor performance when voltage is applied to the source region
Solution Approach 1:
An n-type isolation region is introduced as an intermediary between the p-type body region and the p-type semiconductor substrate. This isolation region electrically disconnects the body region from the substrate, preventing the body effect that occurs when the source region is coupled to internal circuits or resistors. The isolation region acts as a mediator that eliminates the harmful electrical connection while maintaining structural integrity.
Solution Approach 2:
The semiconductor device structure is segmented by dividing the continuous p-type body region-substrate connection into separate regions. The n-type isolation region creates a distinct segmentation that electrically isolates the body region from the substrate, allowing independent control and preventing the propagation of voltage effects from the source to the substrate through the body region.
2Device complexity
If the body region is electrically connected to the substrate, then the device structure is simple, but the driving current is reduced with increasing voltage applied to the source region due to body effect
Solution Approach 1:
The n-type isolation region serves as an intermediary that blocks the electrical path between the body region and substrate. This prevents the body effect from reducing the driving current, allowing the transistor to maintain high current drive capability even when voltage is applied to the source region through external circuits.
Solution Approach 2:
The electrical parameters of the device are changed by introducing the n-type isolation region, which alters the conductivity type in the isolation area. This parameter change creates an electrical barrier that prevents the body effect while maintaining the overall device functionality and high-voltage characteristics.
3Reliability
If a doping region with different conductivity type is introduced to isolate the body region from the substrate, then the body effect is reduced or eliminated, but the device structure becomes more complex
Solution Approach 1:
The invention changes the conductivity type parameter in the isolation region from p-type to n-type, creating an electrical barrier. This single parameter change effectively eliminates the body effect while adding minimal structural complexity, as the isolation region can be formed using standard semiconductor fabrication processes.
Solution Approach 2:
The device structure becomes a composite of different conductivity type regions (p-type body region, n-type isolation region, p-type substrate). This composite structure leverages the properties of different material regions to achieve both electrical isolation and maintained device performance without excessive complexity.
Data Source
Figure 1
Figure 2A~2C
Figure 2D~2E
AI summary
A high-voltage semiconductor device is provided. The device includes a semiconductor substrate having a first conductivity type, and a first doping region having a second conductivity type therein. An epitaxial layer is on the semiconductor substrate. A body region having the first conductivity type is in the epitaxial layer on the first doping region. A second doping region and a third doping region that have the second conductivity type are respectively in the epitaxial layer on both opposite sides of the body region, so as to adjoin the body region. Source and drain regions are respectively in the body region and the second doping region. A field insulating layer is in the second doping region between the source and drain regions. A gate structure is on the epitaxial layer to cover a portion of the field insulating layer.