Power Semiconductor Device Qgd Implant Reduces Gate Charge
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Solution Overview
Problem
Power semiconductor devices face a trade-off between breakdown voltage and on-resistance, where improving one characteristic adversely affects the other, and existing methods to reduce gate charge (Qgd) either increase on-resistance or impact threshold voltage.
Innovation Solution
A MOSgated power semiconductor device with a Qgd implant region of the same conductivity as the base region, positioned to hinder depletion region movement without affecting threshold voltage, which can be easily added during the fabrication process without additional masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the gate oxide thickness is increased to reduce Qgd, then Qgd is reduced, but the device threshold voltage is affected and on-resistance increases
Solution Approach 1:
The patent applies local quality by creating a Qgd implant region with specific doping characteristics in a localized area of the base region, rather than uniformly modifying the entire device structure. This targeted doping approach reduces Qgd through localized charge modification while preserving the threshold voltage characteristics in the channel formation region.
Solution Approach 2:
The patent changes the doping concentration parameter in the base region by forming a Qgd implant region with a doping concentration of at least 1×10^18 atoms/cm³. This parameter change in the base region affects the depletion region behavior and reduces Qgd without significantly impacting the threshold voltage, which is determined by the channel region properties.
2Quantity of substance
If the gate oxide to drift region overlap is reduced to reduce Qgd, then Qgd is reduced, but the device on-resistance increases
Solution Approach 1:
The patent applies local quality by introducing a Qgd implant region in the base region adjacent to the drift region. This localized doping modification reduces the overlap capacitance effect between the gate oxide and drift region, thereby reducing Qgd without requiring changes to the gate oxide-drift region geometric overlap that would increase on-resistance.
3Quantity of substance
If the dopant concentration in the drift region is reduced to reduce Qgd, then Qgd is reduced, but the device on-resistance increases significantly
Solution Approach 1:
The patent applies local quality by creating a Qgd implant region with high doping concentration (at least 1×10^18 atoms/cm³) in the base region, while maintaining the drift region doping concentration. This localized approach reduces Qgd through modified depletion region behavior at the base-drift interface without reducing the overall drift region dopant concentration, thereby preserving low on-resistance.
4Reliability
If buried electrodes are disposed within the trench to deplete the common conduction region, then breakdown voltage is improved, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the doping concentration in the base region through Qgd implantation (at least 1×10^18 atoms/cm³). This parameter change in the base region creates a depletion barrier that improves breakdown voltage characteristics without requiring the addition of buried electrodes within the trench, thereby avoiding increased device complexity.
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
Significantly reduces Qgd by about 40% without impacting on-resistance or threshold voltage, maintaining device performance comparable to conventional trench devices.
Implementation Method 1
the resistivity and the position of the Qgd implant region are selected to hinder the movement of a depletion region into the base region
Implementation Method 2
a Qgd implant region of the same conductivity as the base region formed in the base region
Data Source
AI summary
A power semiconductor device which includes an implant region in the base region thereof to reduce Qgd.