Vertical Power Transistor Doping Structure for Breakdown Voltage
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Solution Overview
Problem
The doping of the drift region in power transistors cannot be increased indefinitely without compromising the breakdown voltage, as higher doping increases the field strength at the body diode, leading to lower breakdown voltage.
Innovation Solution
A vertical power transistor design featuring a drift region with a first doping type and a body region with a second doping type, including trenches and specific doping profiles in first and second areas, which extend perpendicularly into the drift region, creating a compensation structure that reduces field strength at the body diode and maintains high breakdown voltage while minimizing on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the doping in the drift region is increased to minimize the drift region resistance, then the on-resistance is reduced, but the breakdown voltage decreases due to increased field strength at the body diode
Solution Approach 1:
The patent applies local quality by creating first areas with a third doping (opposite charge carrier type) specifically in regions where electrical field peaks occur, while maintaining the original first doping in the drift region. This localized modification reduces field strength at critical points (body diode and trench interfaces) without compromising the overall low on-resistance of the drift region. The selective doping approach allows different regions to have optimized properties for their specific functions.
Solution Approach 2:
The patent implements preliminary action by pre-establishing the compensation doping structure in the first areas before final device operation. The third doping is introduced in advance to counteract the formation of electrical field peaks that would otherwise occur during high-voltage blocking conditions. This preventive measure ensures that when the device operates in high-voltage mode, the field distribution is already optimized to prevent breakdown at the body diode and trench interfaces.
2Loss of energy
If the doping in the drift region is increased to minimize the drift region resistance, then the on-resistance is reduced, but the breakdown strength decreases
Solution Approach 1:
The patent applies local quality by creating first areas with a third doping (opposite charge carrier type) specifically in regions where electrical field peaks occur, while maintaining the original first doping in the drift region. This localized modification reduces field strength at critical points (body diode and trench interfaces) without compromising the overall low on-resistance of the drift region. The selective doping approach allows different regions to have optimized properties for their specific functions.
Solution Approach 2:
The patent converts the harmful effect of high field strength at the body diode and trench interfaces into a benefit by introducing the third doping that creates a compensating charge distribution. The same high doping level in the drift region that causes field peaks is now accompanied by compensation doping in first areas, which transforms the field distribution to be beneficial for both low on-resistance and high breakdown strength.
3Reliability
If field plates are added to improve electric strength and reduce on-resistance, then device performance is enhanced, but device complexity increases
Solution Approach 1:
The patent merges the function of field plates with the trench structure by integrating the field plate directly into the trench formation process. The field plate is positioned within the trench and shares the same structural space, combining two elements (trench and field plate) into a unified structure. This integration reduces the number of separate components and manufacturing steps while maintaining the electric field control benefits of field plates.
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 design achieves a high breakdown strength and low on-resistance, allowing the power transistor to be used in high-voltage applications while preventing electrical field peaks from reaching the body diode, thus optimizing component design and performance.
Implementation Method 1
first areas and second areas, starting from the body region, extend essentially perpendicularly into the drift region. The first areas include a third doping with the second charge carrier type, and the second areas include the first doping with the first charge carrier type. The second doping and the third doping are different.
Data Source
AI summary
A vertical power transistor having front and rear sides. The vertical power transistor includes a drift region that includes a first doping with a first charge carrier type, and a body region that includes a second doping with a second charge carrier type. The body region is situated on the drift region, and includes trenches that extend, starting from the front side, essentially perpendicularly into the drift region. First and second areas are situated between the trenches. The first areas are situated centrally between the trenches, and the second areas are situated between the first areas and the trenches. The first and second areas, starting from the body region, extend essentially perpendicularly into the drift region. The first areas include a third doping with the second charge carrier type, and the second areas include the first doping with the first charge carrier type.