Power MOSFET Cell Layout for Linear-Mode Thermal Stability
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Solution Overview
Problem
Conventional power MOSFETs dissipate higher power in linear-mode applications due to non-uniform die temperature distribution, leading to thermal instability and potential catastrophic failure.
Innovation Solution
A transistor device with interleaved zones of different threshold voltages and variable source region densities, where the body region has multiple doping concentrations and the source region density varies under and around the clip contact area, ensuring uniform temperature distribution and reduced lateral heat flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional power MOSFETs are used in linear-mode applications, then the device can operate in the current saturation region, but the die temperature becomes non-uniform leading to thermal instability and potential catastrophic failure
Solution Approach 1:
The patent applies local quality by creating different source region densities in different areas of the semiconductor substrate. Specifically, a first source region density is implemented in a first area underneath the clip contacting region, while a second source region density is implemented in a second area outside the clip contacting region. This spatial variation in source region density creates corresponding variations in threshold voltage that compensate for temperature gradients, thereby achieving uniform temperature distribution and preventing thermal instability during linear-mode operation.
2Device complexity
If the source region density is uniform across the die, then the device structure is simple, but lateral heat flow causes temperature variations that trigger catastrophic failure
Solution Approach 1:
The patent implements local quality by varying the source region density across different areas of the die. The first source region density is positioned in the first area underneath the clip contacting region, while the second source region density is positioned in the second area outside the clip contacting region. This creates a non-uniform source region structure that generates corresponding threshold voltage variations to counteract lateral heat flow effects, thereby achieving electro-thermal stability without excessive structural complexity.
3Power
If high power dissipation occurs in linear mode, then the transistor can handle high voltage and current, but the rate of power generation exceeds the rate of power dissipation causing thermal runaway
Solution Approach 1:
The patent applies parameter changes by modifying the source region density parameter in different areas of the semiconductor substrate. By implementing a first source region density in the first area and a second source region density in the second area, the invention creates corresponding changes in threshold voltage parameters. These parameter variations enable the device to maintain stable operation under high power dissipation conditions by compensating for temperature-dependent effects, thereby preventing thermal runaway while maintaining high voltage and current handling capability.
Data Source
AI summary
A transistor device includes: a plurality of transistor cells in a semiconductor substrate; and a source pad above the semiconductor substrate and electrically connected to a source region and a body region of the transistor cells. A first group of the transistor cells has a first body region average doping concentration. A second group of the transistor cells has a second body region average doping concentration higher than the first body region average doping concentration. The transistor cells of the first and second groups are interleaved. The transistor cells have a first source region density in a first area of the semiconductor substrate underneath a region of the source pad designated for clip contacting, and a second source region density lower than the first source region density in a second area of the semiconductor substrate outside the first area.