Power Semiconductor Device With Floating Regions And Local Doping
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Solution Overview
Problem
Power semiconductor devices, particularly IGBTs, face challenges in reducing resistance and improving short circuit and breakdown voltage characteristics.
Innovation Solution
The design includes a pair of gate electrodes in trenches with floating regions of a first conductivity type surrounding the trenches, a body region, and a drift region with higher doping concentration between the floating regions, allowing for enhanced base current supply and electric field distribution, which alleviates local temperature rise and improves cell density and short circuit characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the doping concentration of the drift region is increased to reduce resistance, then the on-state voltage decreases, but the breakdown voltage characteristic deteriorates
Solution Approach 1:
The patent applies local quality by creating different doping concentration zones within the drift region. Specifically, it forms a first drift region with higher doping concentration and a second drift region with lower doping concentration at different depths. This allows the lower portion to contribute to current conduction (reducing resistance) while the upper portion maintains the electric field distribution needed for high breakdown voltage, thus resolving the contradiction between low on-state voltage and high breakdown voltage.
2Productivity
If the cell density is increased to improve productivity, then the device size is reduced, but the local temperature rise increases
Solution Approach 1:
The patent changes the doping concentration parameter within the drift region to resolve the contradiction between high cell density and low temperature rise. By forming a deeper drift region with higher doping concentration, the patent enables better current distribution and heat dissipation at the lower portion of the device, allowing higher cell density to be achieved without excessive local temperature rise.
3Quantity of substance
If the maximum doping depth of the body region is increased to improve current capability, then the current conduction is enhanced, but the breakdown voltage decreases
Solution Approach 1:
The patent applies local quality by creating distinct doping concentration zones at different depths. The body region is formed with maximum doping depth that is shallower than the drift region, concentrating the high doping concentration in the lower drift region rather than extending the body region deeply. This allows current capability to be improved through enhanced carrier generation in the body region while maintaining breakdown voltage through the properly structured drift region with extended deeper doping.
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 configuration enhances robustness by forming a base current path, increasing cell density, and mitigating breakdown voltage issues while maintaining high switching capabilities.
Implementation Method 1
a maximum electric field may be generated in a region of a bottom surface of the pair of floating regions having a first conductivity type
Data Source
AI summary
Provided is a power semiconductor device comprising a pair of gate electrodes respectively disposed in a first trench and a second trench spaced apart from each other in a substrate; a body region having a first conductivity type disposed between the first trench and the second trench; a pair of floating regions having a first conductivity type spaced apart from each other and surrounding a bottom surface and at least one side surface of the first trench and the second trench, respectively; and a drift region having a second conductivity type which extends from below the pair of floating regions through a region between the pair of floating regions to the body region, wherein, in the drift region, the doping concentration of a second conductivity type between the pair of floating regions is higher than the doping concentration of a second conductivity type below the pair of floating regions.