IGFET Trench Body Segmentation for Reverse Voltage Blocking
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Solution Overview
Problem
Conventional MOSFETs with schottky contact suffer from increased size and on-resistance due to lateral diffusion of impurities, leading to higher leak currents and reduced drain-source voltage strength, making them unsuitable for compact designs.
Innovation Solution
The design incorporates trenches in the semiconductor substrate to form vertical channels, allowing for reduced thickness of the drain region and prevention of lateral expansion of body regions, along with a schottky barrier diode to control current flow, thereby minimizing on-resistance and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lateral diffusion of impurities is allowed in conventional MOSFET fabrication, then manufacturing process is simpler, but device size increases and on-resistance increases
Solution Approach 1:
The patent divides the semiconductor substrate into distinct regions separated by trenches. The body region is segmented and confined within trench structures, preventing lateral diffusion of impurities while maintaining manufacturing feasibility through standardized trench formation processes.
Solution Approach 2:
The trenches act as intermediary structures that physically separate and isolate the body region from lateral diffusion. These trench structures serve as barriers that prevent impurity spread while allowing the manufacturing process to proceed with conventional techniques.
2Ease of manufacture
If lateral diffusion of impurities is allowed in conventional MOSFET fabrication, then manufacturing process is simpler, but on-resistance increases
Solution Approach 1:
The body region is segmented and confined within trench structures, preventing lateral diffusion of impurities. This segmentation maintains sharp impurity profiles that reduce on-resistance while using conventional trench formation processes.
Solution Approach 2:
The trenches serve as intermediary barriers that prevent lateral diffusion of impurities into the channel region. This isolation maintains optimal doping profiles for low on-resistance while using standard fabrication techniques.
3Reliability
If external diode is connected in series with MOSFET to prevent reverse current, then current control is improved, but device size increases and manufacturing cost increases
Solution Approach 1:
The patent merges the diode function directly into the MOSFET structure by forming a pn junction between the body region and drain region. This integration eliminates the need for separate external diodes while maintaining current control functionality and reducing overall device size.
Solution Approach 2:
The body region serves multiple functions: it provides the channel for MOSFET operation and simultaneously forms the pn junction for reverse current blocking. This multi-functionality eliminates the need for separate diode components while maintaining both switching and protection functions.
4Reliability
If external diode is connected in series with MOSFET to prevent reverse current, then current control is improved, but manufacturing cost increases
Solution Approach 1:
The diode function is merged into the MOSFET fabrication process through integrated pn junction formation. This single integrated structure eliminates the need for separate diode fabrication and assembly steps, reducing manufacturing cost while maintaining current control.
Solution Approach 2:
The body region provides both MOSFET channel function and diode rectification function within a single device structure. This multi-functionality eliminates the need for separate diode components and their associated fabrication costs.
5Reliability
If source electrode is in schottky contact with body region to prevent reverse current, then current control is improved, but device size increases due to lateral diffusion
Solution Approach 1:
The body region is segmented and confined within trench structures, preventing lateral diffusion of impurities. This segmentation maintains compact device dimensions while achieving the current control benefits of schottky contact.
Solution Approach 2:
The trenches act as intermediary barriers that prevent lateral diffusion of impurities from the schottky contact region. This isolation maintains sharp doping profiles and compact device size while enabling effective current control.
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
This approach reduces the size and on-resistance of the IGFET, enhances current control, and prevents parasitic transistor conduction, enabling the device to function as a bidirectional switch with improved antivoltage strength and reduced leakage current.
Implementation Method 1
a gate insulator in each trench; and a gate electrode located in each trench via the gate insulator
Implementation Method 2
gate insulator film 5'
Implementation Method 3
the source electrode is in schottky contact with the body region
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Provided is an IGFET capable of turning off when a reverse voltage is applied. The IGFET includes an n+-type first drain region (6), an n--type second drain region (7), a p-type first body region (8), a p--type second body region (9), an n-type first source region (10a), and an n+-type second source region (10b). Gate insulators (5) and gate electrodes (4) are arranged in trenches (11) formed on a semiconductor substrate (1). The source electrode (3) is in ohmic contact with the n-type first source region (10a) and the n+-type second source region (10b) and in schottky barrier contact with the p-- type second body region (9).