Semiconductor Device Trench End Field Control
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Solution Overview
Problem
In semiconductor diodes with a p-type end layer and a barrier layer, the concentration of the electric field near the trench ends leads to increased reverse recovery loss when the voltage is switched from forward to reverse, as holes flow into the n-type drift layer during forward voltage application, reducing the effectiveness of reverse recovery loss suppression.
Innovation Solution
A semiconductor device design with a p-type end layer extending closer to the second surface than the trench ends, separated by a second trench, and a second p-type layer positioned closer to the second surface than the n-type barrier layer, which suppresses the electric field concentration and prevents hole inflow into the n-type drift layer during forward voltage, thereby reducing reverse recovery loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a p-type end layer is provided to suppress electric field concentration near trench ends, then electric field distribution is improved, but holes flow into the n-type drift layer through the connected p-type layers, increasing reverse recovery loss
Solution Approach 1:
The invention divides the p-type layer structure into two separate segments: a first p-type layer at the upper anode and a second p-type layer at the lower anode, with the n-type barrier layer positioned between them. This segmentation prevents the formation of a continuous p-type conduction path that would allow holes to reach the drift layer, thereby resolving the contradiction between electric field stabilization and reverse recovery loss reduction.
Solution Approach 2:
The n-type barrier layer acts as an intermediary that blocks the flow of holes from the upper p-type layer to the lower p-type layer and subsequently to the n-type drift layer. This intermediary structure maintains the beneficial electric field distribution provided by the p-type end layer while preventing the harmful hole injection that causes reverse recovery loss.
2Stability of the object's composition
If the upper anode layer and lower anode layer are connected by the p-type end layer, then structural continuity is improved, but the potential equalization causes hole inflow into the n-type drift layer, reducing reverse recovery loss suppression
Solution Approach 1:
The invention segments the anode structure into two electrically isolated p-type layers (first and second p-type layers) separated by the n-type barrier layer. This segmentation maintains structural continuity for mechanical support while preventing electrical continuity that would enable hole flow to the drift layer, thus resolving the contradiction between structural and electrical continuity.
Solution Approach 2:
The n-type barrier layer serves as an electrical intermediary that physically connects the upper and lower anode regions structurally while electrically isolating them to prevent hole injection into the drift layer, thereby maintaining structural integrity without compromising reverse recovery performance.
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
The design effectively suppresses reverse recovery loss by maintaining a lower potential for the second p-type layer compared to the first p-type layer, minimizing hole inflow into the n-type drift layer during forward voltage, resulting in reduced reverse recovery current and loss when the voltage is switched to reverse.
Implementation Method 1
the electric field is likely to be concentrated near a longitudinal end of each of the trenches
Implementation Method 2
a p-n junction as an interface between the n-type barrier layer and the lower anode layer becomes a barrier against the holes
Implementation Method 3
When the reverse voltage is applied to the diode, a depletion layer expands within the n-type drift layer, and an electric field is generated in the n-type drift layer
Data Source
AI summary
A semiconductor device includes a semiconductor substrate including, on a first surface, first trenches and a second trench linked to each of the first trenches. The semiconductor substrate includes: a p-type end layer extending from the first surface to a position closer to a second surface of the semiconductor substrate than an end of each of the first trenches on a second surface side and including a longitudinal end of each of the first trenches in a plan view of the first surface; a first p-type layer provided in a region between adjacent first trenches, and contacting the first electrode provided on the first surface; an n-type barrier layer; a second p-type layer. The second trench separates the p-type end layer from the first p-type layer and the second p-type layer.