IGBT Floating Layer Reduces Saturation Voltage
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Solution Overview
Problem
The existing methods for reducing the saturation voltage Vce(sat) in IGBTs with trench-gate structures face a trade-off between lowering saturation voltage and maintaining collector-emitter withstand voltage, as increasing the impurity concentration of the hole barrier layer enhances carrier density but strengthens the electric field at the interface between the body layer and the hole barrier layer.
Innovation Solution
The semiconductor device incorporates a floating layer with a lower impurity concentration placed between the trench electrode and the hole barrier layer, which reduces the electric field strength and allows for a higher impurity concentration in the hole barrier layer, thereby reducing saturation voltage while maintaining withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the impurity concentration of the hole barrier layer is increased to reduce saturation voltage, then carrier density is enhanced and saturation voltage decreases, but the electric field strength at the interface between the body layer and hole barrier layer increases, reducing collector-emitter withstand voltage
Solution Approach 1:
A floating layer with intermediate impurity concentration is introduced between the high-concentration hole barrier layer and the body layer. This floating layer acts as a mediator that gradually transitions the electric field strength, preventing the sharp increase in electric field at the interface while maintaining the high carrier density in the hole barrier layer for low saturation voltage.
Solution Approach 2:
The patent applies local quality by creating distinct regions with different impurity concentrations: the hole barrier layer has high impurity concentration for low saturation voltage, the floating layer has intermediate impurity concentration to manage electric field, and the body layer has its own optimized concentration. Each layer is optimized for its specific function while working together as a whole.
2Reliability
If the impurity concentration of the hole barrier layer is increased to enhance carrier density, then the saturation voltage Vce(sat) is reduced, but the electric field strength at the interface increases, compromising device reliability
Solution Approach 1:
The floating layer serves as an intermediary structure between the high-concentration hole barrier layer and the body layer. It provides a gradual transition zone that reduces the harmful electric field concentration at the interface while preserving the beneficial high carrier density in the hole barrier layer for low saturation voltage operation.
Solution Approach 2:
The floating layer is positioned in advance between the hole barrier layer and body layer to cushion or buffer the electric field before it reaches the critical interface. This preemptive structure prevents the harmful effect of excessive electric field strength from occurring at the body layer interface.
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 effectively reduces the saturation voltage Vce(sat) while preserving the collector-emitter withstand voltage by minimizing the electric field strength between the hole barrier and body layers, allowing for increased impurity concentration in the hole barrier layer.
Implementation Method 1
increases the strength of the electric field at the interface between the body layer 12 and the hole barrier layer 11
Data Source
AI summary
In one embodiment, a semiconductor device includes a semiconductor substrate having an upper surface, a trench electrode placed inside a trench formed on the upper surface, and a trench insulating film placed between the trench electrode and the semiconductor substrate, and the semiconductor substrate includes a drift layer, a floating layer for electric field reduction, a hole barrier layer, a body layer and an emitter layer, and the emitter layer, the body layer and the hole barrier layer are separated from the drift layer by the floating layer for electric field reduction, and a path of a carrier passing through an inverted layer formed in the body layer includes the body layer, the hole barrier layer, a non-inverted region of the floating layer for electric field reduction, and the drift layer.