Nitride Semiconductor Electrode Structure for Field Relaxation
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Solution Overview
Problem
In semiconductor devices using nitride semiconductors, current collapse occurs due to high electric fields, and while field plate electrode structures help disperse the electric field, they increase parasitic capacitance, leading to switching loss. The challenge is to suppress current collapse while minimizing switching loss.
Innovation Solution
A semiconductor device design incorporating a first and second nitride semiconductor layer, electrodes, insulating films, and a conductor with specific edge configurations and capacitance ratios to manage electric field distribution and capacitance, including an extended electrode with portions that enhance field relaxation and reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a field plate electrode structure is used to disperse the electric field, then current collapse is suppressed, but parasitic capacitance increases leading to increased switching loss
Solution Approach 1:
The field plate electrode is divided into multiple segments (first field plate electrode and second field plate electrode) separated by insulating films. This segmentation allows the electric field dispersion function to be maintained while reducing the total parasitic capacitance compared to a continuous field plate structure, thereby suppressing current collapse while minimizing switching loss.
Solution Approach 2:
Insulating films are introduced as intermediary layers between the field plate electrodes and the semiconductor layers. These insulating films act as mediators that reduce the direct capacitive coupling, thereby reducing parasitic capacitance and switching loss while still allowing the field plate structure to disperse the electric field and suppress current collapse.
2Power
If the distance between control electrode and first electrode is reduced, then electric field strength increases improving device performance, but electric field concentration may cause breakdown
Solution Approach 1:
The patent applies different properties to different regions: the first field plate electrode is positioned closer to the control electrode to create a strong electric field in the channel region for high device performance, while the second field plate electrode is positioned closer to the first electrode to disperse the electric field in the drift region and prevent breakdown. This local differentiation of electrode positions optimizes both power and reliability.
Solution Approach 2:
The patent uses vertical stacking of multiple field plate electrodes at different heights and positions to manage electric field distribution. By adding this vertical dimension to the electrode structure, the patent can simultaneously achieve strong electric fields where needed and field dispersion where required, resolving the contradiction between power and harmful field concentration.
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 current collapse and reduces switching loss by optimizing electric field distribution and capacitance, achieving a balance between these two performance metrics.
Implementation Method 1
a phenomenon called current collapse may occur in which the current decreases when a high electric field is applied. To avoid such a phenomenon, a field plate electrode structure is used to disperse the electric field in the element interior.
Implementation Method 2
the field plate electrode structure causes the parasitic capacitance to increase which may cause an increase of the switching loss
Data Source
AI summary
According to one embodiment, a semiconductor device includes a nitride semiconductor layer, a first electrode provided on the layer, a second electrode provided on the layer, a insulating film provided on the layer, a first control electrode provided on the film, and a conductor provided on the film. The first control electrode includes a first edge, and a second edge. The first edge is provided between the second edge and the first electrode. The conductor includes a first portion and a third edge positioned between the first portion and the first electrode. An electric field strength at a first region is substantially equal to an electric field strength at a second region. The first region overlaps the first edge when projected onto a plane perpendicular to a stacking direction. The second region overlaps the third edge when projected onto the plane.